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Axially chiral allenes bearing organoboron groups are highly sought-after building blocks in organic synthesis due to their potential for generating a wide range of axially and centrally chiral molecules. However, the existing methods for preparing axially chiral allenes containing boron group are primarily limited to the synthesis of allenyl boronic esters, and strategies for accessing axially chiral homoallenyl boronic esters are still scarce. Here, we report the general method for synthesizing axially chiral α-boryl-homoallenyl boronic esters through a highly regio- and stereoselective copper-mediated SN2'-addition of newly prepared (diborylalkyl)copper species to chiral propargyl electrophiles. The reaction conditions were optimized to achieve high yields and excellent stereospecificity. The obtained products were successfully transformed into various axially chiral allenes and other chiral molecules by transforming diboron units. The potential for axial-to-central chirality transfer of axially chiral α-boryl-homoallenyl boronic esters is also demonstrated through the stereospecific addition to aldehydes and N-H aldimines, yielding enantioenriched 1,2-oxaborinin-3,5-dienes and 2-aminomethyl-1,3-dienes. Axially chiral allenes are important building blocks in organic chemistry due to their potential for functionalization, which can be enhanced by the presence of a synthetically flexible organoboron group. Here, the authors report a stereospecific synthesis of axially chiral alpha-boryl-homoallenyl boronic esters from enantioenriched propargyl carbonates, mediated by copper. [ABSTRACT FROM AUTHOR]

Site‐selective C−H bond functionalization of arenes at the para position remains extremely challenging primarily due to its relative inaccessibility from the catalytic site. As a consequence, it is significantly restricted to limited molecular scaffolds. Herein, we report a method for the para‐C−H borylation of aromatic aldimines and benzylamines using commercially available ligands under iridium catalysis. The established method displays excellent para selectivity for variously substituted aromatic aldimines, benzylamines and bioactive molecules. Based on several control experiments, it is proposed that a Lewis acid−base interaction between the nitrogen and boron functionality guides the para selectivity via a steric shield for the aromatic aldimines, where Bpin acts as a transient directing group. However, the steric shield of the in situ generated N−Bpin moiety controlled the overall selectivity for the para borylation of benzylamines. [ABSTRACT FROM AUTHOR]

The reaction of 2‐amino‐4,6‐dimethylpyridine with 4‐cyanobenzaldehyde, salicylaldehyde or 2‐hydroxy‐1‐naphthaldehyde furnished the corresponding N‐aryl‐(2‐pyridyl)aldimines in very good yields. The synthetised Schiff bases were characterized by FT‐IR, 1H, 13C, DEPT‐135 and [1H,13C]‐HSQC NMR spectroscopy, HRMS and elemental analyses. Additionally, the structure of 2‐((E)‐(4,6‐dimethylpyridin‐2‐ylimino)methyl)phenol was unambiguously determined by single crystal X‐ray diffraction analysis. Hirshfeld analysis of molecular packing was performed. The most common intermolecular interaction is the hydrogen‐hydrogen (56.8 %) contacts while the most significant interactions are the O...H (6.5 %) and C...C (4.2 %) contacts. DFT calculated geometric parameters and NMR chemical shifts are well correlated with the experimental data. This compound has a net dipole moment of 2.4261 Debye. The MCF‐7 growth was suppressed by N‐aryl‐(2‐pyridyl)aldimines more than that for T47D cell line. The IC50 values of 4‐((E)‐(4,6‐dimethylpyridin‐2‐ylimino)methyl)benzonitrile against MCF‐7 and T47D cell lines were the lowest and it is considered the most promising candidate as anticancer agent. Furthermore, this study conducted a molecular docking of benzonitrile‐based Schiff base onto DNA duplex to explore a potential molecular mechanism for the robust anticancer activities of this Schiff base adduct. The molecular docking results indicate that benzonitrile‐based Schiff base exhibits characteristics of a potential DNA minor groove binder. [ABSTRACT FROM AUTHOR]

The mechanism of 1‐azadienes formation from aldimines and arylacetylenes in the KOtBu/DMSO superbasic medium has been explored theoretically using a DFT approach [B2PLYP(D2)/6‐311+G(d,p)//B3LYP/6‐31+G(d)] and a sophisticated model taking the potassium tert‐butoxide and the nearest solvation shell of the potassium cation explicitly into account. The main focus is placed on (i) a detailed analysis of the kinetic and thermodynamic characteristics of the isomerization of intermediate propargylamine into 1‐azadienes, and (ii) the factors determining the isomeric composition of 1‐azadienes with different substituents in the starting arylaldimines and arylacetylenes. Our findings clearly indicate that the mild experimental conditions of 1‐azadienes formation are accounted for by the relatively small activation barrier (ΔG≠≤16.2 kcal/mol) of the limiting step (ethynylation of aldimine with arylacetylenes). The rapid isomerization of propargylamine to 1‐azadiene is found to be due to low activation barriers (ΔG≠≤9.1 kcal/mol) related to the protons transfer. The isomeric composition in the case of various substituted 1‐azadienes is determined solely by the difference in the thermodynamic stability of the 1E,2E‐ and 1Z,2E‐forms. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Catalytic methylative coupling of internal alkynes and aldehydes/aldimines through regioselective oxidative cyclization promoted by a phosphine–Co complex is presented. Such process constitutes an unprecedented and unique approach for Co‐catalyzed generation of metallacycles that reversed inherent regiochemical biases to furnish a wide range of allylic alcohols and allylic amides bearing a tetrasubstituted alkene in up to 98% yield with high regioselectivity, representing a novel and general strategy for reversal of substrate‐controlled regioselectivity in metal‐catalyzed oxidative cyclization. [ABSTRACT FROM AUTHOR]

Stereodivergent synthesis of N -heterocycle frameworks bearing 1,3-nonadjacent stereogenic centers through a single transformation remains a high-priority challenge in organic synthesis. Herein, we highlight our recent discovery of stereodivergent access to such useful structural motifs using Pd-catalyzed [4+2] annulation reactions of vinyl benzoxazinaones and seven-membered cyclic N-sulfonyl aldimines. A wide range of N -heterocycles with 1,3-nonadjacent stereogenic centers were obtained in high efficiency and stereodivergency. Importantly, the polarity of solvents was found to play a key role in switching the diastereoselectivity. Furthermore, good enantioselectivities of these reactions were achieved by the employment of commercially available Wingphos as the chiral ligand. [ABSTRACT FROM AUTHOR]

Catalytic hydroboration and hydrosilylation have emerged as promising strategies for the reduction of unsaturated hydrocarbons and carbonyl compounds, as well as for the dearomatization of N-heteroarenes. Various catalysts have been employed in these processes to achieve the formation of reduced products via distinct reaction pathways and intermediates. Among these intermediates, N-silyl enamines and N-boryl enamines, which are derived from hydrosilylation and hydroboration, are commonly underestimated in this reduction process. Because these versatile intermediates have recently been utilized in situ as nucleophilic reagents or dipolarophiles for the synthesis of diverse molecules, an expeditious review of the synthesis and utilization of N-silyl and N-boryl enamines is crucial. In this review, we comprehensively discuss a wide range of hydrosilylation and hydroboration catalysts used for the synthesis of N-silyl and N-boryl enamines. These catalysts include main-group metals (e.g., Mg and Zn), transition metals (e.g., Rh, Ru, and Ir), earth-abundant metals (e.g., Fe, Co, and Ni), and non-metal catalysts (including P, B, and organocatalysts). Furthermore, we highlight recent research efforts that have leveraged these versatile intermediates for the synthesis of intriguing molecules, offering insights into future directions for these invaluable building blocks. [ABSTRACT FROM AUTHOR]

This study demonstrates the synthesis of five novel quaternary ammonium aldimines through a two-step synthetic route involving a condensation reaction between 4-pyridincarboxyaldehyde and 3,4,5-trimethoxyaniline, followed by the quaternization of the pyridine N-atom with various aromatic α-bromo ketones. The newly obtained compounds underwent characterization for both purity and molecular structure, utilizing HR-MS, 1D, and 2D NMR spectroscopy in solution, as well as a comparison between single-crystal and powder X-ray analyses in a solid state. The thermal behavior of the studied compounds was evaluated using differential scanning calorimetry (DSC). The antioxidant properties of the compounds were assessed through DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging and ferric-reducing antioxidant power (FRAP) assays, employing Trolox as a standard. The performed in vitro antibacterial screening indicates a selective antibacterial activity against Gram-negative K. pneumoniae and P. aeruginosa, while no such activity is detected for Gram-negative E. coli and Gram-positive S. aureus. [ABSTRACT FROM AUTHOR]

Chiral trisubstituted vicinal diols are a type of important organic compounds, serving as both common structure units in bioactive natural products and chiral auxiliaries in asymmetric synthesis. Herein, by using siloxypropadienes as the precursors of allyl copper(I) species, a copper(I)‐catalyzed diastereoselective and enantioselective reductive allylation of ketones was achieved, providing both syn‐diols and anti‐diols in good to excellent enantioselectivity. DFT calculations show that cis‐γ‐siloxy‐allyl copper species are generated favorably with either 1‐TBSO‐propadiene or 1‐TIPSO‐propadiene. Moreover, the steric difference of TBS group and TIPS group distinguishes the face selectivity of acetophenone, leading to syn‐selectivity for 1‐TBSO‐propadiene and anti‐selectivity for 1‐TIPSO‐propadiene. Easy transformations of the products were performed, demonstrating the synthetic utility of the present method. Moreover, one chiral diol prepared in the above transformations was used as a suitable organocatalyst for the catalytic asymmetric reductive self‐coupling of aldimines generated in situ with B2(neo)2. [ABSTRACT FROM AUTHOR]

The search for efficient and selective methods for the divergent synthesis of multi‐substituted aminotetralins is of much interest and importance. We report herein for the first time the diastereoselective [4+2] annulation of 2‐methyl aromatic aldimines with alkenes via benzylic C(sp3)−H activation by half‐sandwich rare‐earth catalysts, which constitutes an efficient route for the divergent synthesis of both trans and cis diastereoisomers of multi‐substituted 1‐aminotetralin derivatives from readily accessible aldimines and alkenes. The use of a scandium catalyst bearing a sterically demanding cyclopentadienyl ligand such as C5Me4SiMe3 or C5Me5 exclusively afforded the trans‐selective annulation products in the reaction of aldimines with styrenes and aliphatic alkenes. In contrast, the analogous yttrium catalyst, whose metal ion size is larger than that of scandium, yielded the cis‐selective annulation products. This protocol features 100 % atom‐efficiency, excellent diastereoselectivity, broad substrate scope, and good functional group compatibility. The reaction mechanisms have been elucidated by kinetic isotope effect (KIE) experiments and the isolation and transformations of some key reaction intermediates. [ABSTRACT FROM AUTHOR]

The Ti(OPr‐i)4‐mediated three–component condensation of enantiomeric Ellman's amides, dimethylphosphine oxide, and aliphatic, aromatic or heteroaromatic aldehydes proceeds in high yields and diastereoselectivities enabling the rapid, scalable and general asymmetric synthesis of (α‐amino)dimethylphosphine oxide derived compounds bearing alkyl, cycloalkyl or hetaryl group at the chiral carbon atom. Asymmetric synthesis of α‐amino‐α‐polyfluoroalkyl dimethylphosphine oxides was accomplished through diastereoselective addition of dimethylphosphine oxide to enantiomeric Ellman's aldimines, RFCH=NS(O)tert‐Bu (RF=CF3, CHF2, PhCF2). [ABSTRACT FROM AUTHOR]

Five new alkylaluminum complexes with different pyridinyl-substituted imines or cyclohexyl-substituted imines were synthesized and characterized successfully. The aluminum complex [FlCHNCH(CH3)Py]AlMe2(Py = 2-pyridyl) (1) was obtained by reacting 9-[2-pyridyl-CH(CH3)-N＝CH]Fl (Fl = fluorenyl) (L1) and equimolar AlMe3. The reactions of 9-(2-pyridyl-N＝CH)Fl (L2) and 9-[2-N(CH3)2-cyclohexyl-N＝CH]Fl (L3) with equimolar AlMe3 or AlEt3 afforded other alkylaluminum complexes [FlCHNPy]AlMe2(Py = 2-pyridyl) (2), [FlCHNPy]AlEt2 (Py = 2-pyridyl) (3), [FlCHNCyN(CH3)2]AlMe2 (Cy = 2-cyclohexyl) (4) and [FlCHNCyN(CH3)2]AlEt2 (Cy = 2-cyclohexyl) (5). All these complexes (1–5) were characterized using NMR spectroscopy, elemental analysis, and X-ray crystal structure analysis. The catalytic properties of these new alkylaluminum complexes for the hydrophosphonylation of aldimines were examined. Complex 5 showed the best catalytic performance under mild reaction conditions with a low catalyst loading (1 mol%), and 20 different substituents of aldimines were isolated with more than 90% yields. [ABSTRACT FROM AUTHOR]

Catalytic enantioselective Strecker reactions on an achiral substrate using sub-stoichiometric amounts of a chiral catalyst represent an evolving key strategy for the effective synthesis of α-amino nitriles. We herein disclosed the set-up of a flow-based methodology for enantioselective Strecker, employing ethyl cyanoformate as a relatively safe cyanide source, a cinchona-based catalyst, and methanol as additive. A thorough exploration of key parameters allowed the identification of the most efficient reagent mixing mode, the optimum solvent for the flow synthesis, minimum catalyst loading, additive, temperature, and residence time. The newly developed method allows straightforward reaction channeling towards the fast and complete formation of the α-amino nitrile products, thus reducing the yield drop due to indolenine degradation during long-lasting batch-wise reactions. Moreover, we herein provide preliminary hints for sustainability, by proposing a simple procedure for catalyst recycling, thus opening the way for further optimization of the proposed methodology. [ABSTRACT FROM AUTHOR]

Molecular oxygen‐mediated C−H bond alkylation of cyclic aldimines has been reported, which avoids the use of transition metals and additional oxidants. This method allows straightforward access to a series of cyclic aldimine derivatives through a free radical course. Furthermore, this transformation features mild conditions, excellent yields and good functional group tolerance. [ABSTRACT FROM AUTHOR]

cis-5-Arylpyrrolidine-2-carboxylates, obtained by 1,3-dipolar cycloaddition reactions from glycine aryl aldimines and vinyl sulfones, undergo oxidative aromatization under the action of Mn(IV) oxide to form the corresponding 5-arylpyrrole-2-carboxylates in high yields. Factors responsible for the retention of the sulfonyl substituent in the pyrrole backbone were determined. [ABSTRACT FROM AUTHOR]

An efficient approach for the reduction of cyclic N‐sulfonylimines using N‐heterocyclic carbene boranes as the hydride donor was developed, leading to various cyclic sulfamates and sulfonamides in excellent yields. The approach had broad scope including both the N‐sulfonyl aldimines and ketimines under mild reaction conditions, which proves that the NHC‐boranes are good alternatives as the reductive reagents. [ABSTRACT FROM AUTHOR]

The air mediated radical alkylation of cyclic aldimines via autoxidation of alkylboronic acids has been realized under mild reaction conditions. By simply heating cyclic aldimines with alkylboronic acid using air as sole oxidant, this protocol provides a catalyst‐free access to a variety of alkylated cyclic aldimines with 21–91% yields. Preliminary mechanistic studies suggest that a radical pathway might be involved in the reaction. [ABSTRACT FROM AUTHOR]

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Within these, Modes B A b and B C b , in which the boron atom acts as a Lewis acid, have been widely explored, [6] SP , sp [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] whereas reports on the phosphorus atom acting as a Lewis base (Mode B B b ) are scarce. [37] In Ph SB 2 sb PBpin, despite the presence of tricoordinate boron and phosphorus centers, there is negligible -dative interaction between the phosphorus lone pair and the p-orbital on the boron. Keywords: pinacol diphenylphosphinoboronate; boroles; borafluorenes; antiaromaticity; Lewis acid EN pinacol diphenylphosphinoboronate boroles borafluorenes antiaromaticity Lewis acid 2193 2196 4 10/31/23 20231127 NES 231127 Graph Phosphinoboranes [1][52][2] (R SB 2 sb P-BR SB 2 sb ) feature trivalent and tricoordinate P and B atoms linked covalently and are valence isoelectronic with aminoboranes (R SB 2 sb N-BR SB 2 sb ; Scheme 1a). Upon coordination, the P(1)-B(2) bonds of the Ph SB 2 sb PBpin elongate slightly [ B 1 b : 1.953(2) A , B 2 b : 1.9432(18) A , cf. free Ph SB 2 sb PBpin: 1.9274(14) A ]. [Extracted from the article]

This contribution described the chemoselective reduction of secondary carboxamides to aldimines. To perform such challenging transformation, we reported a catalyzed hydrosilylation using Fe(CO)4(IMes) [IMes=1,3‐bis (2,4,6‐trimethylphenyl) imidazol‐2‐ylidene] as the catalyst, diphenylsilane as the reductant under UV irradiation (350 nm) at room temperature for 16 h. Aldimines were then obtained, after a basic quench, in 32–83 % isolated yields. This transformation was unprecedented at iron. [ABSTRACT FROM AUTHOR]

Using a formate salt as a promising hydrogen carrier and one-carbon (C1) source, we have developed a novel and practical method for the preparation of α-amino acid derivatives under mild conditions. In this approach, the photoexcited naphthalene thiolate acts simultaneously as a photoexcited single-electron reductant and a hydrogen atom transfer (HAT) catalyst, enabling efficient metal-free radical–radical cross-coupling of formate with ketimines and aldimines. [ABSTRACT FROM AUTHOR]

A highly enantioselective cyanation of imines (up to >99 % ee) has been developed using well‐designed C2‐symmetric hydrogen bonding catalysts. The catalytic strategy was characterized with low catalyst loading (0.1–1 mol %), easily accessible catalysts with diverse functional groups, and catalytic base additives. A wide range of imines, including the challenging N‐Boc and N‐Cbz protected ketimines and aldimines, as well as fluoroalkylated ketimines, were investigated under mild conditions to afford the products with good to excellent yields (up to 99 % yield) and high enantioselectivity (up to >99 % ee). Control experiments revealed that the multiple hydrogen bonding catalysts enhanced the reactivity and enantioselectivity of the Strecker reaction initiated by the base. [ABSTRACT FROM AUTHOR]

The Schiff base reaction of imidazole-2-carboxaldehydes with the anion of alanine, leucine and phenylalanine in the presence of nickel(II) ion gives the neutral NiL2 complexes. The Schiff base ligand, L, binds through an imidazole nitrogen, NIm, the amino acid nitrogen, NAA, and a carboxylate oxygen, O, atom. The two N2O ligands bind to the nickel(II) in a meridional fashion with the NIm and O of each ligand in trans positions. These ligands can exist as the anticipated aldimine, Im − CH = NAA − CH(R) − CO2−, or the ketimine, Im − CH2NAA = C(R) − CO2−, tautomer. Tautomerization of the initially formed aldimine Schiff base results in movement of the hydrogen atom of the alpha carbon of the amino acid to the aldehyde carbon, CAld, atom of the imidazole carboxaldehyde with resultant relocation of the imine double bond in the reverse direction. Ten structures of the structurally unprecedented ketimine tautomer, prepared from imidazole-2-carboxaldehydes and a pyrazole-3-carboxaldehyde, were presented. The structural data supported the formation of the ketimines in each case, while the aldimine tautomer was observed with imidazole-4-carboxaldehydes. A rationale of this can be explained on the basis of charge distribution in the likely intermediate in the tautomerization. [ABSTRACT FROM AUTHOR]

A highly diastereoselective addition of nitromethane to the C=N bond of enantiomeric fluorine containing Ellman's aldimines, RFCH=NS(O)tert‐Bu (RF=CF3, CF2Br, C2F5, HC2F4), has been successfully developed. The synthetic potential of the resulting β‐nitrosulfinylamides was demonstrated through their conversion into optically active α‐fluoroalkylated 1,3‐nitroamines, 1,3‐diamines, and 4‐fluoroalkylated imidazolidin‐2‐ones. [ABSTRACT FROM AUTHOR]

The first examples of regioselective aryl ortho-C–H functionalization with diphenyldiazomethane for the construction of Caryl–Nhydrazinato bonds were accomplished via the activation of C–H bonds and the subsequent reaction of diphenyldiazomethane with the RE–Caryl bond. The reactions of rare-earth metal monoalkyl complexes LRE(CH2SiMe3)(THF)2 (L = 2,5-[(2-pyrrolyl)CPh2]2(N-Me-pyrrole)) supported by a neutral N-methylpyrrole anchored dipyrrolyl ligand with 2 equiv. of Ph2CN2 gave irreversibly unprecedented hydrazonato-functionalized imino rare-earth metal complexes LRE(Ph2C＝NNC6H4-(o-C＝NHPh) (RE = Y (2a), Lu (2a′)) in good yields involving a rather complex process including the interaction of a diazo unit with a RE–Calkyl bond, a β-H elimination, a N–N cleavage, 1,4-hydrogen transfer and the subsequent C–N coupling with another diphenyldiazomethane. More important is that regioselective aryl C–H bond functionalization with diphenyldiazomethane to construct the Caryl–Nhydrazinato bonds can be easily achieved by three-component reactions of rare-earth metal monoalkyl complexes, a wide range of substituted imines (including aldimines, ketimines or analogous 2-phenylpyridine) and diphenyldiazomethane, affording various hydrazonato-functionalized phenyl, thienyl imino or pyridyl rare-earth metal complexes 2b–2j at room temperature. A further study indicated that the substituents on the phenyl ring have a great effect on the reaction pathway and governed the Caryl–Nhydrazinato bond construction. Moreover, the experimental studies show that the formation of the Caryl–Nhydrazinato bonds is thermodynamically facile, which could be realized at room temperature easily. [ABSTRACT FROM AUTHOR]

A photoredox‐catalyzed umpolung strategy for the synthesis of homoallylamines from unactivated imines and allyl bromides is described. This strategy exploited N,N‐diisopropylethylamine (DIPEA) as an auxiliary agent to indirectly realize the cross‐coupling of imines and allyl bromides. Various sterically hindered homoallylamines were synthesized by combining photocatalysis with halogen atom transfer (XAT). Notable characteristics of this approach include water‐insensitive reaction conditions, high yield (up to 99%), wide substrate scope (suitable for N‐aryl/alkyl and C‐aryl ketimines and aldimines, 39 examples), and high tolerance of functional groups (such as cyano, ester, amide, and thioamide). [ABSTRACT FROM AUTHOR]

Sclareolide was developed as an efficient C-nucleophilic reagent for an asymmetric Mannich addition reaction with a series of N-tert-butylsulfinyl aldimines. The Mannich reaction was carried out under mild conditions, affording the corresponding aminoalkyl sclareolide derivatives with up to 98% yield and 98:2:0:0 diastereoselectivity. Furthermore, the reaction could be performed on a gram scale without any reduction in yield and diastereoselectivity. Additionally, deprotection of the obtained Mannich addition products to give the target sclareolide derivatives bearing a free N-H group was demonstrated. In addition, target compounds 4–6 were subjected to an antifungal assay in vitro, which showed considerable antifungal activity against forest pathogenic fungi. [ABSTRACT FROM AUTHOR]

The fluorine atom is a powerful, yet enigmatic influence on chemical reactions. True to form, fluorine was recently discovered to effect diastereodivergence in an enantioselective aza‐Henry reaction, resulting in a very rare case of syn‐β‐amino nitroalkane products. More bewildering was the observation of an apparent hierarchy of substituents within this substrate‐controlled behavior: Ph>F>alkyl. These cases have now been examined comprehensively by computational methods, including both non‐fluorinated and α‐fluoro nitronate additions to aldimines catalyzed by a chiral bis(amidine) [BAM] proton complex. This study revealed the network of non‐covalent interactions that dictate anti‐ (α‐aryl) versus syn‐selectivity (α‐alkyl) using α‐fluoronitronate nucleophiles, and an underlying secondary orbital interaction between fluorine and the activated azomethine. [ABSTRACT FROM AUTHOR]

The solvent effects in Friedel–Crafts cycloalkylation of epoxides and Cope rearrangement of aldimines were investigated by using ab initio molecular dynamics simulations. Explicit molecular treatments were applied for both reactants and solvents. The reaction mechanisms were elucidated via free energy calculations based on metadynamics simulations. The results reveal that both reactions proceed in a concerted fashion. Key solvent‐substrate interactions are identified from the structures of transition states with explicit solvent molecules. The remarkable promotion effect of hexafluoroisopropanol solvent is ascribed to the synergistic effect of H‐bonding networks and C−H/π interactions with substrates. [ABSTRACT FROM AUTHOR]

Generally, high enantioselectivities (>=85% I ee i ) were achieved in the reaction of variously substituted 2-hydroxyacetophenones B 143 b , such as alkyl-, ethynyl-, as well as ester-substituted ketones (R SP 1 sp =alkyl, ethynyl, CO SB 2 sb Et) which underwent the reaction with 85-93% I ee i . This review is divided into nine parts, dealing successively with enantioselective zinc-catalyzed domino reactions, iron-catalyzed domino reactions, copper-catalyzed domino reactions, scandium-catalyzed domino reactions, nickel-catalyzed domino reactions, magnesium-catalyzed domino reactions, cobalt-catalyzed domino reactions, titanium-catalyzed domino reactions and chromium-catalyzed domino reactions. Keywords: domino reactions; multicomponent reactions; transition metals; first row metals; asymmetric synthesis EN domino reactions multicomponent reactions transition metals first row metals asymmetric synthesis 768 819 52 03/27/23 20230321 NES 230321 This review updates the field of enantioselective domino reactions promoted by chiral catalysts derived from first row metals, such as zinc, iron, copper, scandium, nickel, cobalt, titanium, chromium and magnesium as special case, published since the beginning of 2019. The scope of the reaction was extended to other alkyl halides, such as I i- i C SB 3 sb F SB 7 sb I, which provided by reaction with styrenes and TMSN SB 3 sb , the corresponding chiral fluorinated products B 78 b with moderate to good yields (46-84%) and high I ee i values (78-92% I ee i ). The scope of the domino reaction was extended to other sterically hindered cyclic dienophiles, such as tetrasubstituted cyclopentenones and cyclohexenones B 272 b , which led by reaction with 2-methylbenzaldehydes B 267 b , to the desired cycloadducts B 273 b with variable yields (46-94%) and high I ee i values (88-94% I ee i ). [Extracted from the article]

Simple unhindered aldimines tend to hydrolyze or oligomerize and are therefore spectroscopically not well characterized. Herein we report the formation and spectroscopic characterization of the simplest imino acid, namely glycine imine, by cryogenic matrix isolation IR and UV/Vis spectroscopy. Glycine imine forms after UV irradiation of 2‐azidoacetic acid by N2 extrusion in anti‐(E,E)‐ and anti‐(Z,Z)‐conformation that can be photochemically interconverted. In matrix isolation pyrolysis experiments with 2‐azidoacetic acid, glycine imine cannot be trapped as it further decarboxylates to aminomethylene. In aqueous solution glycine imine is hydrolyzed to hydroxy glycine and hydrated glyoxylic acid. At higher concentrations or in the presence of FeIISO4 as a reducing agent glycine imine undergoes self‐reduction by oxidative decarboxylation chemistry. Glycine imine may be seen as one of the key reaction intermediates connecting prebiotic amino acid and sugar formation chemistry. [ABSTRACT FROM AUTHOR]

The stereocontrolled synthesis of 1-substituted homotropanones, using chiral N-tert-butanesulfinyl imines as reaction intermediates, is described. The reaction of organolithium and Grignard reagents with hydroxy Weinreb amides, chemoselective N-tert-butanesulfinyl aldimine formation from keto aldehydes, decarboxylative Mannich reaction with β-keto acids of these aldimines, and organocatalyzed L-proline intramolecular Mannich cyclization are key steps of this methodology. The utility of the method was demonstrated with a synthesis of the natural product (−)-adaline, and its enantiomer, (+)-adaline. [ABSTRACT FROM AUTHOR]

The first ZnCl2-catalyzed alkynylation of aldimines with tetra(phenylethynyl)tin was achieved under solvent-free conditions. The present methodology provides propargylamines in 38–62% yields. [ABSTRACT FROM AUTHOR]

Reaction of [Ru(dmso)4Cl2] with N-(4′-R-phenyl)pyrrole-2-aldimines (abbreviated as HL-R; where H depicts the dissociable pyrrole N–H proton and R = OCH3, CH3, H and Cl) in refluxing toluene in the presence of triethylamine has afforded a family of complexes of type [Ru(L-R)2(dmso)2]. The crystal structures of all four complexes have been determined, which show that the aldimine ligands are chelated to the metal center as an N,N-donor and the dmso's are coordinated through sulfur. The relative thermodynamic stability of the five possible geometric isomers of these complexes has been assessed with the help of DFT calculations, and the tcc-isomer (tcc depicting the pyrrole-nitrogens to be trans, the imine-nitrogens cis, and the S-coordinated dmso's cis) is found to be the most stable isomer. The isolated complexes also have the tcc geometry, as observed in their crystal structures. The coordinated dmso's are found to be displaceable by chelating bidentate ligands (depicted as L-L) to furnish mixed-tris complexes of type [Ru(L-R)2(L-L)], as demonstrated through isolation of two such complexes (with R = OCH3, and L-L = 2,2′-bipyridine or 1,10-phenanthroline). Optimization of their structures and probing into the thermodynamics of their formation have been done by the DFT method. Electronic spectra of all six complexes, recorded in dichloromethane solution, show intense absorptions in the visible and ultraviolet regions, which have been analyzed by the TDDFT method. Cyclic voltammetry of all the complexes in acetonitrile solution shows ruthenium-based oxidative response(s) within 0.77–1.24 V vs. SCE, and ligand (bpy/phen) based reductions within −1.06 to −1.70 V vs. SCE in the case of the [Ru(L-R)2(L-L)] complexes. [ABSTRACT FROM AUTHOR]

Manganese‐catalyzed hydrogenation reactions have aroused widespread interest in recent years. Among the catalytic systems described, especially PNP‐ and NNP–Mn pincer catalysts have been reported for the hydrogenation of aldehydes, ketones, nitriles, aldimines and esters. Furthermore, NNP−Mn pincer compounds are efficient catalysts for the hydrogenolysis of less reactive amides, ureas, carbonates, and carbamates. Herein, the synthesis and application of specific imidazolylaminophosphine ligands and the corresponding Mn pincer complexes are described. These new catalysts have been characterized and studied by a combination of experimental and theoretical investigations, and their catalytic activities have been tested in several hydrogenation reactions with good to excellent performance. Especially, the reduction of N‐heterocycles can be performed under very mild conditions. [ABSTRACT FROM AUTHOR]

Secondary phosphine chalcogenides mildly (no catalysts and solvents, 20–65 °C, 0.25–65.5 h) react with aldimines to deliver the hitherto unknown α‐aminophosphine oxides, sulfides and selenides in good to excellent yields. [ABSTRACT FROM AUTHOR]

• Detailed quantitative analysis of the different intermolecular interactions present in methyl (E)-2-(2-hydroxybenzylidene)hydrazine-1-carboxylate (a), methyl (E)-2-(3- hydroxybenzylidene)hydrazine-1-carboxylate (b) and methyl (E)-2-(4- hydroxybenzylidene)hydrazine-1-carboxylate (c). • The structure investigation revealed that various interactions like C H...O, N H...O and pi stacking interactions are involved in constructing ring motifs to stabilize the crystal packing. • Their solid-state structures have been analysed through Hirshfeld surface analysis, including the evaluation of the different energy frameworks, indicating that the molecular structures are primarily formed by hydrogen bonds and the stabilization is dominated via the electrostatic energy contribution. • The chemically active regions of the aldimines were identified by the analysis of molecular electrostatic potential surface. • Further, from PASS analysis and literature reports, molecular docking of title compounds was carried out with testosterone 17beta-dehydrogenase (NADP+) (PDB-ID 3KLP). Interactions present in differently substituted hydroxy based imine derivatives were characterised and identified by the utilisation of spectroscopic techniques in conjunction with X-ray crystallography and theoretical computations. All the target compounds ' a - c ' crystallises in monoclinic crystal system with P21/c and C2/c space groups. CH...Pi and Pi...Pi interaction are the characteristic interactions present in the target compounds ' a - c ' The most significant contributions to the crystal packing were found using Hirshfeld surface analysis, and potential contact points were identified. H...H, O...H and C...H contacts and π stacking interactions are the dominant contacts observed in all the crystals these results showed that hydrogen bonding and hydrophobic interactions were significantly present. Furthermore, investigations related to calculations of the molecular electrostatic potential and frontier molecular orbital (highest occupied–lowest unoccupied) were carried out for the optimised structure. The HOMO-LUMO energy gap made it possible to determine the molecule's chemical hardness, chemical inertness, electronegativity, and electrophilicity index, which showed its possible kinetic stability and reactivity. The target compounds' predicted activity spectra (PASS) showed that these compounds exhibit significant Testosterone 17beta-dehydrogenase (NADP+) inhibition activity, with Pa 7.18–7.95. Finally, Testosterone 17beta-dehydrogenase (NADP+) (PDB-ID 3KLP) was used to conduct molecular docking investigations of compounds ' a - c '. Due to their tiny size and lack of rigidity, which enable them to bind well at any position, a and b exhibit higher binding free energies of -7.08 and -7.00 kcal/mol and inhibition constants of 0.1 and 1.2 µM than compound c. [Display omitted] [ABSTRACT FROM AUTHOR]

An efficient and reliable method has been developed for chemo-selective synthesis of Schiff bases (SB) (3a–n) by using Baker’s yeast (BY) as biocatalyst. The reaction is highly chemo-selective as only benzaldehydes take part in the reaction, whereas acetophenones fail to take part in this reaction. Furthermore, it was observed that amino acids (glycine, phenylalanine & tryptophan) and aliphatic amines (isopropyl amine and 1-amino butane) did not take part in the reaction. The present method is very efficient as it involves simple work up and gives the products in good to excellent yield. The reaction is totally carried out under eco- friendly and environmentally begin conditions by using ethanol (EtOH) as a green solvent. Thus it is anticipated that the present newly developed method will open a gateway for the chemist to prepare the selective SB (Aldimines) in the presence of ketones in facile and eco-friendly conditions.

A bifunctional tertiary amine-squaramide-catalyzed enantioselective Mannich-type addition of available allomaltol to N-protected aldimines was developed. The resulted adducts were readily transformed into non-proteinogenic α-amino acids and their derivatives were not easily accessible by other methods via oxidative fragmentation, esterification, amidation and deprotection reactions. The absolute (S)-configuration of the thus obtained α-amino acids was established by comparison of the N-Ts-PheGly optical rotation sign with the reported data. [ABSTRACT FROM AUTHOR]

The article presents a study on a catalytic asymmetric reductive/deoxygenative alkynylation of secondary amides. Topics discussed include the scope of the reaction and chemoselectivity, alkynes and functional group tolerance of the rection, the extension to N-benxylamides, and synthetic applications of the reaction.

A sequential phosphine‐catalyzed asymmetric [3+2] annulation of aldimines with allenoates and oxidative central‐to‐axial chirality transfer strategy has been developed. This approach is operationally simple, allowing for rapid access to a range of axially chiral CF3‐containing 2‐arylpyrroles with high enantiomeric excess. Furthermore, an atroposelective synthesis of esaxerenone is presented, illustrating the practical potential of the reported method. [ABSTRACT FROM AUTHOR]

Through-bond conjugation (TBC) and/or through-space conjugation (TSC) determine the photophysical properties of organic luminescent compounds. No systematic studies have been carried out to understand the transition from aromatic TBC to non-aromatic TSC on the photoluminescence of organic luminescent compounds. In this work, a series of small aromatic and aliphatic aldimines were synthesized. For the aromatic imines, surprisingly, N,1-diphenylmethanimine with the highest TBC is non-emissive, while N-benzyl-1-phenylmethanimine and N-cyclohexyl-1-phenylmethanimine emit bright fluorescence in aggregate states. The aliphatic imines are all emissive, and their maximum emission wavelength decreases while the quantum yield increases with a decrease in steric hindrance. The imines show concentration-dependent and excitation-dependent emissions. Theoretical calculations show that the TBC extents in the aromatic imines are not strong enough to induce photoluminescence in a single molecule state, while the intermolecular TSC becomes dominant for the fluorescence emissions of both aromatic and aliphatic imines in aggregate states, and the configurations and spatial conformations of the molecules in aggregate states play a key role in the formation of effective TSC. This study provides an understanding of how chemical and spatial structures affect the formation of TBC and TSC and their functions on the photoluminescence of organic luminescent materials. [ABSTRACT FROM AUTHOR]

Today, multi-component reactions (MCRs) are known for their many benefits, including time and cost savings, atom economy, notable structural diversity and molecular complexity. To optimize the reaction conditions, the three component reaction of ethyl cyclopropanecarboxylate, aniline and benzaldehyde was taken as a model. In summary, herein is reported a convenient three-component reaction of ethyl cyclopropanecarboxylate, aniline derivatives and aromatic aldehydes for the synthesis of new ethyl 1,2-diarylpyrrolidine-3-carboxylate derivatives in very good yields. [Extracted from the article]

Cyclic anhydrides, including sulfur-embedded anhydrides such as thiodiglycolic anhydride, are useful dipolar synthons for the synthesis of complex organic molecules through formal cycloaddition reactions with imines (i.e., the Castagnoli–Cushman Reaction (CCR)). Here, we disclose that a disulfide-embedded anhydride (i.e., dithiodiglycolic anhydride) unexpectedly underwent an efficient formal cycloaddition with aryl aldimines to afford functionalized 4-thiazolidinones, without complications arising from the CCR. Importantly, when 1,3-azadienes were employed, the 2-alkenyl-4-thiazolidinones were obtained without complications stemming from the sulfa-Michael reaction or the Tamura reaction. These 4-thiazolidinones constitute the core of several pharmaceuticals that display a broad spectrum of biological activities, including anti-HIV and anticancer. The current tactic obviates the need for thioglycolic acid, an alternative annulation partner associated with a strongly unpleasant odor. The ensuing N,S-heterocycles are then engaged in several selective fragment growth processes, including oxidation to sulfoxides, sulfones, and epoxysulfones. [ABSTRACT FROM AUTHOR]

Aldimine derivatives chromophores grafted on polyacetylene oligomers were first designed to investigate the nonlinear optical (NLO) response of the resulting materials using CAMB3LYP method. The effects of different factors such as the chain length separating the substitutions as well as the configurations and the orientations of these latter, were examined and discussed. In a second part of this paper, NLO responses, in particular the static hyperpolarizabilities of polyvinyl oligomers substituted by aldimine chromophores via carboxylic groups and by pyrrolidone groups were calculated for different configurations. The stability and the hydrogen bonding in each oligomer were also discussed. [ABSTRACT FROM AUTHOR]

Six iron(0) tricarbonyl complexes (1a–f) with a η4-1-azadiene moiety were prepared and their performance in the hydroboration of unsaturated organic compounds was investigated. All the complexes exhibit catalytic activity towards hydroboration of ketones, aldehydes and aldimines with pinacolborane (HBpin) as a hydride source to lead to secondary alcohols, primary alcohols, and secondary amines, respectively, after hydrolysis of the hydroboration products. Of the iron(0) tricarbonyl complexes, complex 1e is the most robust one and was employed throughout the catalytic investigation. Its preference towards the three types of substrates is as follows: aldimines > aldehydes ≫; ketones. In total, 24 substrates were examined for the catalytic hydroboration reactivity and generally, isolation yields ranging from 40% to 95% were achieved. Mechanistic investigation suggests that the catalytic hydroboration of the substrates proceeds via intramolecular hydride transfer without going through an Fe–H intermediate. As indicated by 1H NMR spectroscopic monitoring, the substrates and the borane agent bind to the iron centre and the imine N atom, respectively, which facilitates the hydride transfer by activating the B–H bond and polarizing the double bond of the substrates. [ABSTRACT FROM AUTHOR]

A novel N‐heterocyclic carbene (NHC)‐promoted regiodivergent protocol for exo (2‐OH) and endo (5‐OH) isosorbide (IS) imidates synthesis is described. The disclosed strategy allows the straightforward synthesis of monoimidate‐isosorbides (MIIs) endowed with the biologically relevant benzothiazole (BTA) moiety under mild oxidative conditions, starting from easy‐accessible aldimines. Process optimization encompassed the use of stoichiometric diquinone as well as atmospheric oxygen as oxidant species, focusing on reaction dichotomy between oxidative and oxygenative pathways. The reaction scope was investigated on a representative selection of BTA‐containing aldimines and further extended to congeners bearing different biologically pivotal N‐heterocyclic rings (benzoxazole, thiazole and isoxazole), observing good levels of yield (up to 87 %) and regioselectivity (exo/endo up to 10.0; endo/exo up to 7.0). Furthermore, the employment of an immobilized‐NHC under heterogeneous conditions was assessed, showing satisfactory selectivity towards exo‐MIIs (exo/endo=3.8). Overall, the methodology presented provided an unprecedented collection of high value‐added products with potential applications in different fields. [ABSTRACT FROM AUTHOR]

A convenient procedure of synthesis of N-carbamoyl-protected propargylic amines substituted with a cyclopropyl group from α-amido sulfones and cyclopropylacetylene is described. The reaction is catalyzed by a chiral BINOL-type zinc complex and provides the corresponding products in good yields and enantioselectivities. [ABSTRACT FROM AUTHOR]

• Detailed quantitative analysis of the different intermolecular interactions present in (E)−1-(((3-nitrophenyl)amino)methylene)naphthalen-2(1H)-one ( a ), (E)−5-(diethylamino)−2-(((3-nitrophenyl)imino)methyl)phenol( b ) and (E)−2-(((3-nitrophenyl)imino)methyl)phenol ( c ). • The structure investigation revealed that various interactions like C H...O, N H...O and pi stacking interactions are involved in constructing ring motifs to stabilize the crystal packing. • Their solid-state structures have been analyzed through Hirshfeld surface analysis, including the evaluation of the different energy frameworks, indicating that the molecular sheets are primarily formed by hydrogen bonds and the stabilization is dominated via the electrostatic energy contribution. • The chemically active regions of the Schiff base molecules were identified by the analysis of molecular electrostatic potential surface. • Further, from PASS analysis and literature reports, molecular docking of title compounds was carried out with internal ribosome entry site of Hepatitis C virus ED42 (PDB-ID 3T4B). We have synthesized and thoroughly analyzed many intermolecular interactions present in (E)-1-(((3-nitrophenyl)amino)methylene)naphthalen-2(1H)-one (a), (E)-5-(diethylamino)-2-(((3-nitrophenyl)imino)methyl)phenol(b) and (E)-2-(((3-nitrophenyl)imino)methyl)phenol (c). Compounds a (keto-amine tautomeric form) and b, which have one molecule in the asymmetric unit, crystallize in the monoclinic crystal system with space groups P21/n and C2/c, respectively. Compound C, on the other hand, crystallizes in an orthorhombic crystal structure with the space group Pca21. The structural analysis showed that the construction of ring motifs to stabilize the crystal packing involves several interactions, including pi stacking interactions, N H...O, and C H...O interactions. Hirshfeld surface analysis has been used to examine their solid-state structures, including the evaluation of several energy frameworks. The results show that hydrogen bonds play a major role in the formation of the molecular sheets, and that electrostatic energy contribution dominates stability. Using fingerprint plots, it was possible to examine the variations and commonalities in the target compounds' relative contributions from noncovalent interactions. In addition, B3LYP hybrid functional with 6- 311 G (d, p) level basis set was used in the density functional theory computations to optimize the structural coordinates. Through the examination of the molecular electrostatic potential surface, the chemically active areas of the target imine molecules were located. Additionally, using the internal ribosome entry site of the Hepatitis C virus ED42 (PDB-ID 3T4B), molecular docking of the title compounds was performed based on PASS analysis and literature findings. [Display omitted] [ABSTRACT FROM AUTHOR]