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Achieving high molecular complexity can be not trivial, but the exploitation of domino reactions provides an atom‐ and step‐economical method to reach this target. Over the past decades, a lot of efforts have been put on the development of photocatalytic cascades employing both metal‐based and purely organic catalysts. Despite the effectiveness of these protocols, catalyst‐ and additive‐free light‐induced domino reactions are gaining momentum thank to their efficiency, operational simplicity and sustainability. The increasing number of papers published on this field in the last years is a proof of the appeal of these transformations. In this Review, we discuss domino and multicomponent reactions mediated by light with a focus on photocatalyst‐ and additive‐free processes. The most recent advances in the synthesis of complex nitrogen‐, oxygen‐, sulphur‐ and selenium‐heterocycles together with multicomponent cascades are analysed with an emphasis on both experimental and mechanistic studies. [ABSTRACT FROM AUTHOR]

In the last 25 years, the influence of microwave (MW) irradiation in chemical synthesis has intrigued chemists for the exceptional results obtained in shortening reaction times. Inspired by recent papers that demonstrate the existence of a non‐thermal effect in some MW assisted reactions, we examine herein a series of reactions catalysed by homogeneous and heterogeneous metals occurring under MW irradiation. The review contains examples of hydroformylation, hydrogenation (including enantioselective versions with 98 % ee), hydrogenolysis, hydrogen transfer and borrowing hydrogen reactions carried out under MWs and metal catalysis. An increase in the influence of MW irradiation was often observed in reactions performed with heterogeneous catalysts such as Pd/C. In these cases, a "microwave catalysis" can be possible. The increase in the (apparent) reaction rate requires the contribution of MW irradiation that modifies the catalyst surface, driving the reaction progress as occurring in other kinds of catalysis. [ABSTRACT FROM AUTHOR]

In this paper, the optimization of the synthesis of 3,7‐bis(N‐methyl‐N‐phenylamino)phenothiazinium chloride with a detailed analysis of reaction parameters, i.e. solvent, temperature, amount of amine, as well as addition of a non‐nucleophilic base, is presented. Spectroscopic, electrochemical and computational data show that the presence of the two phenyl rings, directly bound on the PTZ+ core, inhibits the aggregation ability of the salt at concentrations up to 10–3 M. Furthermore, the introduction of an aromatic group in phenothiazinium‐based molecules appears strategic to introduce other useful functionalities, thus opening new opportunities in the drug design/discovery research field. [ABSTRACT FROM AUTHOR]

The paper outlines a synthetic approach towards novel spacer‐extended bis‐ene‐yne structures via a tandem thiophene ring‐opening reaction to selectively obtain the Z,Z‐isomers. Various unsaturated spacer moieties are matter of interest in these investigations owing to potential applications in organic electronics. As a result, the successful application of the tandem ring‐opening process on a representative set of spacer‐extended substrates is demonstrated and the limitations regarding substrate and product scope are revealed in terms of ring‐opening ability and stability. Additionally, a general oxidation protocol for ene‐yne compounds capable of accessing double‐sided sulfone species is developed. The comparison of the photophysical and electronic properties before and after oxidation reveals significant effects of the chemical modification on the intrinsic characteristics of the materials and thus a wide variability of the developed molecular building blocks. [ABSTRACT FROM AUTHOR]

In this paper we outline how dihalohydration reactions of propargylic alcohols can be used to access a wide variety of useful halogenated building blocks. A novel procedure for dibromohydration of alkynes has been developed, and a selection of dichloro and dibromo diols and cyclic ethers were synthesized. The dihalohydration of homo‐propargylic alcohols provides a useful route to 3‐halofurans, which were shown to readily undergo cycloaddition reactions under mild conditions. Finally, a novel ring expansion of propargylic alcohols containing a cyclopropylalkyne provides access to halogenated alkenylcyclobutanes. [ABSTRACT FROM AUTHOR]

In this paper a new phosphorus-free catalyst for the Morita-Baylis-Hillman reaction is disclosed. A bicyclic imidazolyl alcohol having a Lewis basic center associated with a hydrogen-bond donor group was used as catalyst for the reaction. Aliphatic cycloalkanones such as 2-cyclopentenone and 2-cyclohexanone and aliphatic and aromatic aldehydes were used successfully, and the reaction was found to work nicely using water as solvent in the presence of a phase-transfer additive. [ABSTRACT FROM AUTHOR]

Although the aldol condensation is a well-known reaction, the aza-type aldol condensation, namely, the intra-molecular condensation of common keto lactams leading to bicyclic vinylogous lactams, is a highly demanding transformation, with potential applications in both organic synthesis and medicinal chemistry. The known methods for this type of cyclization require several steps. In this paper, we disclose a straight-forward approach that consists of the in-situ formation of silyl enol ethers with tert-butyldimethylsilyl trifluoromethanesulfonate (TBDMSOTf ), lactam activation with triflic anhydride (Tf2O), and a tandem cyclocondensation reaction. The reaction can be run in a one-pot manner or in a two-step fashion, both under mild conditions. The yields for the one-pot version were 52-80%. In some cases, the two-step version gave higher overall yields (44-85%) than the one-pot version. [ABSTRACT FROM AUTHOR]

The synthesis and herbicidal efficacy of a novel library of fully substituted 3‐hydroxypyrazoles is reported. An efficient, divergent approach to introduce phenyl, phenoxy, phenylsulfanyl, anilino and benzyl substituents in the 4‐position of the pyrazole, alongside a flexible synthesis of N1‐alkyl analogues is described via final step diversification of key intermediates. Herbicidal screening of the prepared compounds against key weed species identified the lead compound 2‐[4‐(2,4‐difluorophenoxy)‐1,5‐dimethyl‐pyrazol‐3‐yl]oxy‐5‐fluoropyrimidine, which was prepared on a multi‐gram scale using an optimised synthetic route. [ABSTRACT FROM AUTHOR]

The photoreactivity of a series of hitherto unknown, multiply fluorinated 2‐azidobenzimidazole derivatives was investigated. The synthesis of the starting material includes regioselective p‐defluorination of nitrobenzene derivatives employing Ogoshi's conditions. If the 6‐position was unsubstituted, irradiation in the presence of N‐protected amino acids at 300 nm (Rayonet) led to the formation of arylesters by oxygenation of the 6‐position in good to excellent yields and perfect regioselectivity. We did not observe any displacement of fluoride. If the 6‐position itself was fluorinated, alternative positions of the benzene portion were attacked. Mechanistically, the reaction proceeds through ring opening of the singlet nitrene to the cyanodiimine or via the iminobenzimidazolium ion. The availability of a set of fluorinated photo‐adducts prompted the quantum chemical calculation of their 19F NMR chemical shifts. Even with the most suitable method investigated (ωB97XD/TApr‐cc‐pVDZ), deviations of up to 5 ppm from the experimental values were observed, underlining the importance of experimental measurements. [ABSTRACT FROM AUTHOR]

We report a direct C-H to C-C bond functionalization of electron-deficient heteroaromatics enabled by mild C-C bond cleavage of cyclopropanols as a new route to β-aryl carbonyl-containing products. Additionally, as an alternative to using a 'catalyst' that requires an excess amount of a sacrificial oxidant for regeneration and/or oxidative aromatization, this paper features manganese(IV) oxide as an inexpensive 'dual role' reagent - effecting both C-C bond cleavage and ultimate rearomatization. Under the specified conditions, a variety of heterocycles proved competent for regioselective C-C bond formation, alongside a diverse array of cyclopropanols with broad functional-group tolerance. We highlight applications to complex-molecule synthesis and direct derivatization of biologically active alkaloids. Furthermore, kinetic isotope effect (KIE) experiments, radical scavengers, and some insight into the application of tri- and tetravalent manganese species are invoked to shape an initial mechanistic hypothesis. [ABSTRACT FROM AUTHOR]

3‐Acyl‐4‐hydroxypyan‐2‐ones with pendent furans, readily available from dehydroacetic acid, are substrates for intramolecular [4+4]‐photocycloaddition. In the presence of stoichiometric lithium base, these substrates undergo conversion to lactone‐bridged cyclooctenones in moderate to good yields upon irradiation in THF at 0 °C. In contrast to other crossed [4+4]‐photocycloadditions of pyran‐2‐ones, these examples proceed with complete diastereoselectivity for the endo cycloadducts. [ABSTRACT FROM AUTHOR]

A new structural family of benzothiazocines bearing two or three carbon stereogenic centers on the 8-membered ring was synthesized by intramolecular Cu-catalyzed N-arylation. The chiral racemic 1,3-aminothioethers precursors have been prepared from easily available starting materials. An ionic organic base was used for the first time in an intramolecular C􀀀 N coupling, in medium-ring series, leading to higher yields than those obtained with an inorganic base, and a partial epimerization in some cases. The synthetic sequence was successfully performed on one example in asymmetric version, demonstrating the accessibility of enantioenriched benzothiazocines. [ABSTRACT FROM AUTHOR]

We have investigated the stereoselective formation of spiro oxindole pyrrolidines via formal [3+2] cycloaddition of oxindole imines with ketoesters and ketoamides. Bifunctional squaramide organocatalyst was able to induce enantioselectivity of up to 60 % ee, increased to 72 % ee after re‐crystallization, in the formation of spiro pyrrolidines with ketoesters. Interestingly, ketoamides provided alternative spiro oxindole pyrrole products in addition to the main product, which was formed via a different reaction pathway. Structures of spiro oxindole pyrrolidine as well as pyrrole products were confirmed by X‐ray crystallographic analysis. Two new squaramide based catalysts were synthesized and tested. DFT calculation helped elucidate the reaction course. [ABSTRACT FROM AUTHOR]

The synthesis of allocolchicine analogues is of importance as these compounds have been found to possess promising anticancer activity by affecting tubulin polymerization. In this paper, the synthesis of 28 novel substituted 6-oxa-allocolchicinoids is reported. The key steps involved in the synthesis were a Suzuki-Miyaura coupling reaction, followed by an acid-catalyzed intramolecular transacetalization to afford the desired 5-alkoxy-5,7-dihydrodibenzo[ c, e]oxepines. In addition, when thiophenol and phenol were used in the transacetalization step, the 5-(phenylsulfanyl)-5,7-dihydrodibenzo[ c, e]oxepine and 4-(5,7-dihydrodibenzo[ c, e]oxepin-5-yl)phenol skeletons were obtained, respectively. The cytotoxicity of the synthetic compounds was unfortunately not impressive; however, one of the compounds was shown to sensitize vincristine-resistant leukemia and lymphoma cells to vincristine, a result vindicating further synthetic studies. [ABSTRACT FROM AUTHOR]

Transition‐metal‐free and site‐selective C–H selenylation of heterocyclic N‐oxides with diselenides is described. This method can be also applied for the formation of C2‐sulfenylated and C2‐tellurinated quinoline derivatives. Notably, the simple reaction conditions with the use of anisole as a green solvent have been employed in this coupling reaction. Combined mechanistic investigations elucidate a plausible reaction mechanism of this process. The synthetic transformations demonstrate the utility of the developed method. [ABSTRACT FROM AUTHOR]

The assembly of enzymatic cascades and multi‐step reaction sequences represents an attractive alternative to traditional synthetic‐organic approaches. The biocatalytic reaction mediators offer not only mild conditions and permit the use of environmentally benign reagents, but the high compatibility of different enzymes promises more streamlined reaction setups. In this study, a triple‐enzymatic strategy was developed that enables the direct conversion of γ,δ‐unsaturated esters to N‐hydroxy‐γ‐lactam building blocks. Hereby, a lipase‐catalyzed hydroxylaminolysis generates hydroxamic acid intermediates that are subsequently aerobically activated by horseradish peroxidase and glucose oxidase to cyclize in an intramolecular nitroso ene reaction. Utilizing the hydroxylaminolysis/ene‐cyclization sequence for the preparation of an aza‐spirocyclic lactam, the multi‐enzymatic methodology was successfully employed in the synthesis of key intermediates en route to alkaloids of the Cephalotaxus family. [ABSTRACT FROM AUTHOR]

The iron‐catalyzed oxidative C−C homocoupling of diarylamines affords 2,2′‐bis(arylamino)‐1,1′‐biaryls which represent crucial synthetic building blocks for an access to a range of seven‐membered heterocyclic ring systems. Reaction with paraformaldehyde, diphenyl carbonate, and diphenyl sulfite as efficient 1,1‐dielectrophiles led to dibenzo[d,f][1,3]diazepines, dibenzo[d,f][1,3]diazepinones, and dibenzo[c,e][1,2,7]thiadiazepine 6‐oxides. The synthetic procedures enable short and practical routes to these 1,3‐diazepine derivatives under mild reaction conditions and with a high tolerance of various functional groups. [ABSTRACT FROM AUTHOR]

Isocytosine has two stable tautomers, which can form a dimer with each other, stabilised by three intermolecular hydrogen bonds similar to those in the guanine–cytosine base pair. Molecules with suitable donor/acceptor hydrogen‐bonding patterns can form intermolecular complexes with one or the other isocytosine tautomer. These intermolecular interactions stabilise the selected isocytosine tautomer, leading to an increase of its relative concentration. The integration of the 1H NMR spectra acquired at various temperatures and concentrations was used for the determination of free‐energy changes of the formation of the isocytosine dimer/complex. The experimental free‐energy changes contain contributions from the formation of the isocytosine dimer/complex itself and from the rearrangement of the solvation shell. The latter contribution was estimated through a comparison of the experimental free‐energy changes with those calculated for the dimer/complex formation at the DFT level. The study demonstrates that the molecular environment can change relative tautomer stabilities, which supports the hypothesis of the involvement of rare nucleobase tautomers in the catalytic function of RNA enzymes. Isocytosine tautomers can form a dimer with each other that are stabilised by three intermolecular hydrogen bonds. Molecules with suitable donor/acceptor hydrogen‐bonding patterns can form intermolecular complexes with one or the other isocytosine tautomer, leading to an increase of its relative concentration. [ABSTRACT FROM AUTHOR]

Iodosobenzene (PhIO) is a well-known hypervalent iodine reagent for its Lewis acidic oxidizing capability. In recent times it has been repeatedly proven to be a powerful tool for the development of toxic, costly transition-metal-free advanced and impressive methodologies to construct diverse array of different heterocycles. In this review some selected viable and innovative strategies from 2007 to 2016 have been contemplated. Sometimes mechanistic proposals were also taken as prime consideration since synthetic organic chemists are providing fresh stimuli to reinforce the theoretical predictions to grasp the unique nature of PhIO in dissimilar conditions. Convenient and environmentally friendly cyclization and cycloaddition protocols were delineated adequately to integrate the practical findings and mechanistic points of view. [ABSTRACT FROM AUTHOR]

Herein, we report a simple synthesis of disubstituted pyrazino-oxazines with controlled stereochemistry using readily available building blocks: N-Fmoc-protected α-amino acids and 2-bromo ketones. The convenient solid-phase synthesis afforded polymer-supported derivatives of N-alkylated N-acylated tert-butylserine, which were subjected to spontaneous cyclative cleavage to yield the corresponding pyrazine intermediates. The target 1,7,8,9a-tetrahydropyrazino[2,1-c][1,4]oxazine-6,9-diones were obtained in two steps by acid-mediated cleavage of the tert-butyl group followed by cyclization of the oxazine scaffold. [ABSTRACT FROM AUTHOR]

In 1982, Buckley et al. reported on the hydroxy-functionalized derivative of 6,13-diazapentacene (DAP), namely 5,12-dihydroxo-6,13-diazapentacene. In an attempt to reproduce the synthetic procedure, 1H NMR and 13C{1H} NMR spectroscopic data revealed the formation of a constitutional isomer of the supposed compound. A single-crystal X-ray structure determination revealed that the actual structure of the dark-violet product was 6-amino-5H-dibenzo[a,h]phenoxazin-5-one (2), a benzo[a]phenoxazine derivative. These kinds of compounds are, along with a wide range of pharmacological applications, known for their specific fluorescent properties, which were analyzed for compound 2. Furthermore, it was shown that 2 can be utilized as reagent for the synthesis of other benzo[a]phenoxazine derivatives, herein 6-(dimethylamino)-5H-dibenzo[a,h]phenoxazin-5-one (3). [ABSTRACT FROM AUTHOR]

A series of new heteroannulated pyrido[2,3-c]coumarins have been prepared by the domino reactions of chromone-3-carboxylic acid derivatives with electron-rich binucleophilic aminoheterocycles. The products contain the core structures of coumarin, pyridine, and an annulated five-membered heterocyclic system, namely pyrazole, pyrrole, or isoazole. The fluorescence of the products was investigated. The products inhibit ecto-5′-nucleotidase (e5′NT) enzymatic activity. [ABSTRACT FROM AUTHOR]

Benzil and its derivatives naphthil and pyridil have been found to undergo a dianionic oxy-Cope rearrangement upon reaction with 2-lithio-4,5-dihydrofuran to give 3,3'-octahydrobifuranyls selectively as the meso diastereomers. The diastereoselectivity is explained based on the reaction mechanism and the conformation of the starting material. 4,4'-Di-tertbutylbenzil gave the respective intramolecular aldol adduct, whose relative configuration was determined by NOE experiments. [ABSTRACT FROM AUTHOR]

Highly diastereo- and enantioselective 1,3-dipolar cycloadditions between functional ketonitrones and β-substituted enals are promoted by MacMillan imidazolidinium organocatalysts. A study of the reaction scope shows that high selectivities are conserved if the N-protecting group or the ester function is varied. However, the reaction is sensitive to steric interactions with the C substituent of the nitrone. In all cases, the reaction proceeds with high exo selectivity. In most cases, a third diastereomer, incompatible with a concerted mechanism, was also observed, albeit in minute amounts. DFT calculations suggest that the cycloaddition proceeds in a nonconcerted fashion by an initial oxa-Michael-type addition of the nitrone to the double bond followed by a cyclization. This mechanism explains the formation of the observed minor diastereomers. In addition, the diastereo- and enantioselectivities of the reaction were shown to be intermediately thermodynamically controlled, and the diastereomeric ratio is modulated by the kinetics of iminium hydrolysis. [ABSTRACT FROM AUTHOR]

Here described an acid‐controlled regional diverse synthesized process of CF3‐containing ketoimines by the condensation of benzo[b]thiophene‐2,3‐dione and 2,2,2‐trifluoroethlamine. The imines obtained at either the 2‐position or 3‐position can be further used as substrates in asymmetric organocatalyzed [3+2]‐cycloaddition reactions, leading to a library of regiodiverse bispiro‐compounds with 85–96 % yield and 65–99 % ee. [ABSTRACT FROM AUTHOR]

An organocatalytic asymmetric synthesis of directly linked benzothiazole‐dihydroimidazoles with two adjacent tertiary‐quaternary stereocenters through a Mannich‐type reaction of isocyanoacetates with N‐(2‐benzothiazolyl)imines is disclosed. When employing bifunctional dihydroquinine‐derived squaramide as catalyst, moderate to excellent yields (up to 97 % yield), moderate diastereoselectivities and excellent enantioselectivities (up to >99 % ee) were obtained for a variety of substrates. In addition, the transformation of the resulted directly linked benzothiazole‐dihydroimidazole into highly functionalized α,β‐diamino esters was also demonstrated. [ABSTRACT FROM AUTHOR]

Incorporation of tellurium into polycyclic compounds may endow them with unique chemical and optoelectronic properties which are not observed in their lighter chalcogen analogues. Herein, a telluropyran‐containing polycyclic compound (T1) synthesized through a ring‐expansion reaction from the corresponding tellurophene analogue can be reversibly oxidized into halogen adducts T1•X2 (X=Cl, Br, I) with the formation of two Te−X bonds. Their chemical structures have been verified by two‐dimensional 1H‐1H correlation spectroscopy and single crystal X‐ray diffraction analysis. The halogen oxidations of T1 and the reverse thermal eliminations as well as the halogen exchange in halogen adducts T1•X2 have been systematically investigated and compared by UV‐vis absorption titration, electrochemical measurements, thermogravimetric analysis, and density functional calculations (DFT). The oxidation of Te(II) in T1 to Te(IV) in T1•X2 results in the switch from aromaticity to nonaromaticity for the six‐membered telluropyran ring, as revealed by nucleus‐independent chemical shift calculations. It is also found that the halides in the halogen adducts can be exchanged by lighter ones, but not vice versa. The stabilities of the oxidized products are in the order of T1•Cl2>T1•Br2>T1•I2, which are consistent with the calculated rate constants and energy barriers of the elimination reactions. [ABSTRACT FROM AUTHOR]

Herein, we report the design and synthesis of a series of novel cationic nitrogen‐embedded polyaromatic hydrocarbons with a planar geometry. The synthetic pathway is based on catalytic C−C/C−H bond activation relay that enabled preparation of regioselectively 5,6,10,11‐tetrasubstituted naphtho[2,1,8‐ija]quinolizinium salts bearing various types of substituents. Single‐crystal X‐ray analyses of selected compounds confirmed planarity of the quinolizinium core. Most of the prepared compounds exhibited strong fluorescence (Φs up to >99 %) ranging from 420–600 nm depending on the substitution pattern. According to DFT calculations LUMO is always distributed over the quinolizinium framework regardless of the attached substituents, whereas delocalization of HOMO is related to the substitution pattern. Electrochemical measurements show irreversible reduction of all compounds, which is supported by the calculated location of LUMO orbitals. [ABSTRACT FROM AUTHOR]

A stereoselective one‐pot double derivatization of cyclobutene‐1‐carboxylic acid via a mild organic base catalyzed amidation/aza‐Michael addition of benzo[d]oxazol‐2(3H)‐ones has been developed. This unprecedented tandem reaction provides access to novel β‐N‐heterocyclic cyclobutane carboximide derivatives with a trans geometry. The carboximide moiety reacts smoothly with nucleophiles, allowing access to diverse derivatives of trans‐β‐N‐heterocyclic cyclobutanecarboxylic acid, including peptidomimetic structures. [ABSTRACT FROM AUTHOR]

Cyclopenta‐, benzo‐, and cyclohepta[b]‐annulated azepane scaffolds were prepared in two steps from optically active cyclic α‐allyl‐β‐oxoesters. The first step was ruthenium‐catalyzed olefin cross metathesis with acrylonitrile. The second step was palladium‐catalyzed dihydrogenation which consists of three consecutive processes: The hydrogenation of the C−C double and C−N triple bonds was followed by the reductive amination via the iminium ion formed in situ from the primary amino function and the endocyclic carbonyl group. This last step gave, stereoselectively, the annulated azepanes with relative trans‐configuration. The amino function and the ester group define two points for further diversification of the scaffolds. The trifluoroacetyl derivatives allowed to establish the enantiopurity of the products to be 97–98 % ee by GLC on a chiral phase. The relative trans‐configurations and in one case also the absolute (R,R)‐configuration was established by X‐ray crystallography. [ABSTRACT FROM AUTHOR]

The one‐bond nucleophilic reactivities of seven cyclic α‐diazo carbonyl compounds in dichloromethane were determined by analyzing the kinetics of their reactions with benzhydrylium ions (one‐bond reference electrophiles) at 20 °C according to the Mayr‐Patz equation. Though not calibrated for pericyclic reactions, the identified nucleophilicities also reflect relative reactivities of the α‐diazo carbonyl compounds in 1,3‐dipolar cycloadditions with dimethyl acetylenedicarboxylate. These (3+2)‐cycloadditions primarily gave spirocyclic 3H‐pyrazoles, which underwent thermal [1,5]‐sigmatropic (van Alphen‐Hüttel) rearrangements to furnish 1H‐pyrazole‐fused tricyclic products. [ABSTRACT FROM AUTHOR]

Novel N‐substituted pyrrolo[3,4‐b]quinoline‐1,3‐diones have been prepared via a highly chemoselective palladium‐catalyzed carbonylative imidazation‐cyclization reaction in a one‐pot synthetic approach. This methodology, which has been applied for the first time to access such original scaffolds through two different protocols involving 3‐bromo‐2‐iodoquinoline, as a typical partner, primary amines, and atmospheric or high carbon monoxide pressure (20 bar), has shown an excellent tolerance for many functional groups. The use of bidentate ligands such as XantPhos and dppp, either under atmospheric or high‐pressure conditions, provides a wide range of carbonylated compounds in good to excellent yields (up to 82 %). Furthermore, some new quinoline‐2,3‐dicarboxamides have been isolated as side products in very low yields and have been fully characterized. The solid state structures of three of the synthesized acridinimides have been unequivocally established by single‐crystal XRD analysis. [ABSTRACT FROM AUTHOR]

Herein, we report a novel protocol for the direct synthesis of 1,3‐oxathiolan‐5‐ones based on the (3+2)‐cycloaddition between thioketones and acetylenedicarboxylic acid. The products were obtained in a one‐pot reaction within short reaction times and in typically very good yields. The product structure was confirmed by X‐ray diffraction analysis. [ABSTRACT FROM AUTHOR]

Herein, we present a straightforward strategy for the synthesis of fused heterocycles through a deoxygenative, intramolecular Minisci‐type reaction. This approach grants access to complex polycyclic scaffolds in three steps from readily available starting materials, such as chlorinated heteroarenes and 1,3‐diols. The use of saccharide derivatives as the starting 1,3‐diol motif allows for the synthesis of novel heterocyclic scaffolds with excellent diastereoselectivity and formal retention of configuration at the newly formed C−C bond. [ABSTRACT FROM AUTHOR]

The regioselective lithiation of 1,2,3‐triazoles provides an opportunity to introduce additional functionality, however this simple functionalisation strategy using triazoles bearing electron‐withdrawing N‐substituents has not been investigated until now. Herein, we demonstrate that the lithiated triazole intermediates can readily decompose, even at −78 °C. In addition, lithiation‐deuteration studies reveal lithiation can take place competitively on both the triazole and the electron‐withdrawn aryl ring. Careful control of reaction conditions is therefore required to i) minimise decomposition pathways; and ii) facilitate regioselective functionalisation of the triazole. [ABSTRACT FROM AUTHOR]

An efficient and simple procedure for the preparation of 2‐pyridinone is reported. The obtained products contained various bicyclic 2‐pyridinones and multi‐substituted 6‐amino‐2‐pyridinones. This approach employed 3‐hydroxy‐2‐aryl acrylate and nitro ketene aminal as substrates, and the corresponding 2‐pyridinones were obtained in good to excellent yields. This method may be used for the synthesis of bicyclic 2‐pyridinones, as well as multi‐substituted complex 2‐pyridinones. [ABSTRACT FROM AUTHOR]

A series of 5-phosphonoisoxazoline N-oxides were prepared in good to excellent yields by selective O-alkylation of nitronate anions with (a-tosyloxyvinyl)phosphonates. A comprehensive study was undertaken to limit the competitive for-mation of the (β-nitrocyclopropyl)phosphonate resulting from C-alkylation of the ambident nitronate anions. The 5-phosphonoisoxazoline N-oxides thus formed were reduced to the corresponding 5-phosphonoisoxazolines. [ABSTRACT FROM AUTHOR]

A series of 5-phosphonoisoxazoline N-oxides were prepared in good to excellent yields by selective O-alkylation of nitronate anions with (α-tosyloxyvinyl)phosphonates. A comprehensive study was undertaken to limit the competitive formation of the (β-nitrocyclopropyl)phosphonate resulting from C-alkylation of the ambident nitronate anions. The 5-phosphonoisoxazoline N-oxides thus formed were reduced to the corresponding 5-phosphonoisoxazolines. [ABSTRACT FROM AUTHOR]

The synthesis of fused polycyclic heteroaromatics was achieved via successive vinylic/aromatic carbon−fluorine (C−F) bond activation. The Suzuki‐Miyaura coupling of (1‐bromo‐2,2‐difluorovinyl)biaryls with 2‐hydroxy‐ or 2‐aminophenylboronic acids (esters) followed by defluorinative 5‐endo‐trig cyclization yielded 2‐fluorobenzofurans (indoles) with a biaryl moiety in one‐pot operation. The obtained 2‐fluorobenzoheteroles underwent acid‐mediated intramolecular C−F/C−H coupling to yield tetra‐, penta‐, and hexacyclic heteroaromatics. This protocol allowed the synthesis of various substituted benzo‐fused dibenzofurans and carbazoles. [ABSTRACT FROM AUTHOR]

A convenient and efficient method for one pot synthesis of polysubstituted (Z)‐halobenzo[c,d]indoles from 8‐alkynyl‐1‐naphthylamine derivatives using CuCl2 and CuBr2 as the halogenated reagents has been developed. In this protocol, both (Z)‐chloro and bromobenzo[c,d] indole derivatives can be obtained in moderate to good yields by copper halide‐promoted stereoselective intramolecular cis‐addition annulation reactions. A novel fluorescent molecule with AIE properties was constructed via Suzuki coupling reaction and its optical properties was investigated, which made them possible candidates for optoelectronic conjugated materials. [ABSTRACT FROM AUTHOR]

PhI(OAc)2/CuI‐promoted ring rearrangement of 1,3‐azasilinyl‐4‐epoxides has been developed. The reaction proceeds by a Si−C bond migration/oxidation process, leading to structurally novel 2‐silamorpolines containing an aryl/aldehyde groups‐substituted quaternary carbon. [ABSTRACT FROM AUTHOR]

Pyridineacetic acids undergo dimerization under action of the activating agents, giving rise to 2‐hydroxy‐3‐(pyridin‐2‐yl)‐4H‐quinolizin‐4‐ones. The introduction of a difluoroboryl bridge into such derivatives leads to novel highly fluorescent compounds. [ABSTRACT FROM AUTHOR]

Various isocyanide‐based multicomponent reactions prove to be highly reliable when β‐substituted β‐amino boronic esters are employed as the amine component, allowing the efficient synthesis of unprecedented peptidomimetics and heteroatom‐rich boron‐containing small molecules. In particular, the scope of the Ugi reaction is widely exploited, to give a family of enantiopure β‐substituted β‐amido boronates. The Ugi‐azide and the van Leusen reactions allow to joint together prominent pharmacophoric moieties, such as β‐amino boronic acids on one side, and tetrazole or imidazole rings on the other side, realizing a successful application of the molecular hybridization concept. [ABSTRACT FROM AUTHOR]

Tandem C−H‐arylation and C−H‐amidation of cis‐cinnamyl hydroxamatesusing a single metal catalyst (and air as oxidant) leads to the formation of 3‐aryl‐2‐quinolone ring system in a regioselective manner. The corresponding trans‐isomer under identical conditions gives rise to 4‐aryl‐2‐quinolone derivative.The complementary regioselectivity observed during tandem C−H‐arylation C−H‐amidation of isomeric substrates is unusual and of potential application. [ABSTRACT FROM AUTHOR]

Cascade reactions of 1,3‐diarylpropane‐1,3‐dione or unsaturated ketones with arylsulfonyl hydrazide have been achieved in the presence of iodine source. Fully substituted C4‐sulfenylated pyrazoles were synthesized via the tandem pyrazole annulation and C(sp2)−H sulfenylation. This approach is efficient and practical. The starting materials are readily available, while also providing a useful strategy for the construction of different arylthio‐substituted pyrazole skeletons. [ABSTRACT FROM AUTHOR]

A systematic investigation of ethynyl N‐heterocycle‐substituted‐λ3‐iodanes (ENHIs) is presented. In a straightforward one‐pot synthesis these novel reagents can be obtained in high yields bearing a variety of N‐heterocycles. Their reactivity as electrophilic alkyne group transfer reagents was benchmarked in well‐established and novel inter‐ and intramolecular group transfer reactions. [ABSTRACT FROM AUTHOR]