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Electrochemically induced efficient and economical method has been developed for synthesis of β-phosphono malononitriles via condensation of various aldehyde, malononitrile and phosphite esters at room temperature. The present protocol highlights cost efficient, one pot, easy work-up and environmentally benign process. [ABSTRACT FROM AUTHOR]

The [3+2] cycloaddition (32CA) reaction of an azomethine ylide (AY), derived from isatin and L-proline, with phenyl vinyl sulphone has been studied within Molecular Electron Density Theory (MEDT) at the ωB97X-D/6-311G(d,p) level. ELF topological analysis of AY classifies it as a pseudo(mono)radical species with two monosynaptic basins at the C1 carbon, integrating a total of 0.76 e. While vinyl sulphone has a strong electrophilic character, AY is a supernucleophile, suggesting a high polar character and low activation energy for the reaction. The nucleophilic Parr functions indicate that the pseudoradical C1 carbon is the most nucleophilic center. The 32CA reaction presents an activation Gibbs free energy of 13.1 kcal·mol−1 and is exergonic by −26.8 kcal·mol−1. This reaction presents high endo stereoselectivity and high meta regioselectivity. Analysis of the global electron density transfer (GEDT) at the most favorable meta/endo TS, 0.31 e, accounts for the high polar character of this 32CA reaction, classified by forward electron density flux (FEDF). A Bonding Evolution Theory (BET) study along the most favorable meta/endo reaction path characterizes this 32CA reaction, taking place through a non-concerted two-stage one-step mechanism, as a pseudo(mono)radical-type 32CA reaction, in agreement with the ELF analysis of the AY. [ABSTRACT FROM AUTHOR]

Azacycles such as indoles and tetrahydroquinolines are privileged structures in drug development. Reported here is an unprecedented regiodivergent intramolecular nucleophilic addition reaction of imines as a flexible approach to access N‐functionalized indoles and tetrahydroquinolines, by the control of reaction at the N‐terminus and C‐terminus, respectively. Using ketimines derived from 2‐(2‐nitroethyl)anilines with isatins or α‐ketoesters, the regioselective N‐attack reaction gives N‐functionalized indoles, while the catalytic enantioselective C‐attack reaction affords chiral tetrahydroquinolines featuring an α‐tetrasubstituted stereocenter. Mechanistic studies reveal that hydrogen‐bonding interactions may greatly facilitate such unusual N‐attack reactions of imines. The utility of this protocol is highlighted by the catalytic enantioselective formal synthesis of (−)‐psychotrimine, and the construction of various fused aza‐heterocycles. [ABSTRACT FROM AUTHOR]

A new donor-π-acceptor derived from phenothiazine, namely 2-(2-((10-hexyl-10H-phenothiazin-3-yl)methylene)-3-oxo-2,3-dihydroinden-1-ylidene) malononitrile (PTZON) was synthesized and fully characterized, and its potential as a fluorescent sensor for cyanide anion was investigated. The PTZON showed a visible absorption band at 564 nm corresponds to an intramolecular charge transfer (ICT) and an emission band at 589 nm in CH3CN/H2O. The results of cyanide anion titration revealed ratiometric changes in both absorption and fluorescence spectra as a result of the nucleophilic addition of cyanide anion via Michael addition. The optical studies, FT-IR spectra, NMR, high-resolution mass, and DFT calculations confirmed the sensing mechanism. The selectivity of PTZON as a cyanide anion fluorescent sensor was proved in mixed solvent solutions, and the sensitivity was as low as 0.011 µM, which is far lower than the value allowed by the United States Environmental Protection Agency for drinking water (1.9 µM). Also, the detection limit of PTZON was assessed to be 3.39 μM by the spectrophotometric method. The binding stoichiometry between PTZON and cyanide anion was found to be 1:1 as evidenced by mass spectra. TLC silica-coated plates test strips demonstrated the fluorescent detection of cyanide anion. [ABSTRACT FROM AUTHOR]

• N-doped defective graphene (N)G has three types of N atoms, including pyridinic ones. • CO 2 and NH 3 adsorption on (N)G reveals the presence of acid and basic sites. • (N)G promotes Michael addition of methylene active compounds to unsaturated ketone. • (N)G promotes the Henry addition of nitromethane to benzaldehyde. • DFT calculations indicates that the most basic sites are pyridinic N atoms at the edge. N-doped defective graphene [(N)G] obtained by pyrolysis at 900 °C of chitosan contains about 3.7% of residual N atoms, distributed as pyridinic, pyrrolic and graphitic N atoms. It has been found that (N)G acts as basic catalyst promoting two classical C C bond forming nucleophilic additions in organic chemistry, such as the Michael and the Henry additions. Computational calculations at DFT level of models corresponding to the various N atoms leads to the conclusion that N atoms are more stable at the periphery of the graphene sheets and that H adsorption on these sites is a suitable descriptor to correlate with the catalytic activity of the various sites. According to these calculations the most active sites are pyridinic N atoms at zig-zag edges of the sheets. In addition, N as dopant changes the reactivity of the neighbour C atoms. Water was found a suitable solvent to achieve high conversions in both reactions. In this solvent the initial distribution of N atoms is affected due to the easy protonation of the N Py to N PyH sites. As an effect, C edge sites adjacent at N PyH with an appropriate reactivity towards the α-C-H bond breaking are formed. The present results show the general activity of N-doped graphene as base catalysts and illustrate the potential of carbocatalysis to promote reactions of general interest in organic synthesis. [ABSTRACT FROM AUTHOR]

An approach to cyclic nitrones from N‐hydroxylactam derivatives is documented. The nucleophilic addition of an organolithium reagent to an N‐OSEM [SEM=2‐(trimethylsilyl)ethoxymethyl] lactam forms a five‐membered chelated intermediate, which undergoes both elimination and deprotection to give a fully substituted nitrone in a one‐pot process. When combined with the N‐oxidation of easily available chiral lactams, this method becomes especially useful for the quick synthesis of chiral nitrones in enantio‐pure form, enabling the concise total synthesis of cylindricine C. [ABSTRACT FROM AUTHOR]

A novel strategy for the expedient construction of CF3‐embeded tertiary/quarternary carbon centers was developed by taking advantage of photoredox catalysis. Thanks to a key step of single‐electron oxidation, electron‐rich gem‐difluoroalkenes, which otherwise are essentially reluctant towards F‐nucleoplilic addition, now readily participate in this fluoroallylation reaction. Furthermore, this strategy provides an elegant example for the generation, as well as functionalization, of α‐CF3‐substituted benzylic radical intermediates using cheap and readily available starting materials. [ABSTRACT FROM AUTHOR]

Allylzinc reagents were used to access highly functionalized tertiary carbinamine derivatives in high yields from cyanoesters and cyanocarbonates. While the monoaddition of organometallics on nitriles is generally observed, in this work the nucleophilic allylation occurs twice, due to an intermediate transfer of the carbonyl moiety onto the nitrogen atom. The chemoselectivity of the reaction allows the presence of various functionalities and in the case of carbonate derivatives, the nature of the final product was modulated by kinetic control, giving selectively hydroxyamides or cyclic carbamates. [ABSTRACT FROM AUTHOR]

A general one-pot procedure for the 1,2-addition of organolithium reagents to amides followed by the Buchwald–Hartwig amination with in situ released lithium amides is presented. In this work amides are used as masked ketones, revealed by the addition of organolithium reagents which generates a lithium amide, suitable for subsequent Buchwald–Hartwig coupling in the presence of a palladium catalyst. This methodology allows for rapid, efficient and atom economic synthesis of aminoarylketones in good yields. [ABSTRACT FROM AUTHOR]

Chiral tertiary alcohols are an important class of organic compounds which have found wide applications in both academia and industry. Therefore, various synthetic strategies towards these compounds have already been developed. Among them, the catalytic asymmetric addition of carbon nucleophiles to ketones is the most desirable route owing to its straightforwardness as well as its economic, efficient and versatile advantages. This review summarizes and discusses the recent achievements in this field classified according to the reaction types. Special attention is paid to the mechanisms, advantages and limitations of each reaction. In addition, the applications of these catalytic processes in the synthesis of related natural products, pharmaceuticals or their analogues are briefly discussed as well. [ABSTRACT FROM AUTHOR]

Cyclodipeptide 2,5‐diketopiperazines (DKP) are privileged structural units present in drugs and natural alkaloids. This work reports a new method for the synthesis of biologically important DKP scaffolds based on an intramolecular nucleophilic α‐addition of general amides towards an alkynamide system. The utility of this umpolung cyclization mediated by trimethyl phosphine and l‐glutamic acid is highlighted by its application to the concise total syntheses of 6‐methoxyspirotryprostatin B (the first total synthesis), spirotryprostatin A, and spirotryprostatin B. Alkaloid synthesis: This work reports a concise and practical approach towards the synthesis of spirotryprostatins. This synthetic route features an organo‐mediated intramolecular umplolung cyclization to construct the DKP ring system, a Grignard addition‐dehydration‐Friedel–Crafts reaction procedure to establish the C‐ring and the prenyl moiety, and a regioselective oxidation and microwave‐assisted stereospecific rearrangement to afford the spiro‐oxindole system. [ABSTRACT FROM AUTHOR]

A method for the synthesis of N‐trifluoroacetyl amides through trifluoroacetic anhydride transfer to nitrones by borrowing and returning oxygen atom is reported. The reaction appears to proceed via electrophilic trifluoroacetylation, followed by nucleophilic addition and elimination, and intramolecular substitution, affording N‐trifluoroacetyl amides in good to excellent yields. The present method tolerates a wide range of functional groups. Also, nitrones react with difluoroacetic anhydride providing the corresponding N‐difluoroacetyl amides. Moreover, the method described could be of interest from a biological point of view, because it constitutes a straightforward strategy for the synthesis of biologically active N‐trifluoroacetyl amide analogues. A variety of N‐trifluoroacetyl amides are obtained from trifluoroacetic anhydride transfers to nitrones through borrowing and returning oxygen atom. This transformation proceeds smoothly under mild conditions via electrophilic trifluoroacetylation, followed by nucleophilic addition and elimination, and intramolecular substitution. Furthermore, the method also provides efficient access to N‐difluoroacetyl amides. This work presents a straightforward access to the valuable N‐fluoroacetyl amides from readily available and inexpensive starting materials. [ABSTRACT FROM AUTHOR]

A quantitative synthesis of piperine from commercially available starting material is presented. The synthesis relies on a stereoselective nucleophilic attack of an in situ generated cuprate onto a cyclobutene lactone. The so-formed aryl-substituted cyclobutene spontaneously undergoes a conrotatory 4π-electrocyclic ring opening to form the 4-aryl pentadienoic acid as a single diastereoisomer. The high-yielding synthesis can be easily modulated on the aryl and on the amide moiety for the synthesis of a wide range of piperine analogues. [ABSTRACT FROM AUTHOR]

Nucleophilic radical additions at innately electrophilic C(sp2) centers are perfectly suited for the direct functionalization of heterocycles. Using bench stable and commercially available alkyl oxamate and oxamic acid derivatives in combination with photoredox catalysis, a direct carbamoylation of heterocycles yielding amide functionalized pharmacophores in a single step is reported. The reaction conditions reported are compatible with structurally complex heterocyclic substrates of pharmaceutical interest. Notably, derivatives containing functional groups incompatible with standard amidation reactions, such as carboxylic acids and unprotected amines, were found to be amenable to this reaction paradigm. Non‐obvious amide: Bench stable and commercially available alkyl oxamates are used for the direct C−H carbamoylation of heterocycles by using visible‐light photoredox mediated conditions. This method yields amide functionalized pharmacophores in a single step and is amenable with derivatives having functional groups incompatible with standard amidation reactions. [ABSTRACT FROM AUTHOR]

(E)-(3-Aryl-3-oxoprop-1en-1-yl)triphenylphosphonium bromides reacted with arylhydrazines in an acidic medium to form hydrazones, the intramolecular heterocyclization of which led to the formation of (2,5- diaryl-2,3-dihydro-1H-pyrazol-3-yl)triphenylphosphonium bromides. Under the action of hydrobromic acid, the resulting quaternary phosphonium salts produced saturated (3-aryl-3-oxopropyl)triphenylphosphonium salts. [ABSTRACT FROM AUTHOR]

Abstract A novel colorimetric fluorescent chemosensor TP1 with a D-π-A structure for the detection of (cyanide) CN− has been developed. TP1 is capable of showing high selectivity and sensitivity towards CN− over a wide range of other interfering anions. After reaction with CN−, TP1 shows a significant blue-shift of absorption peak from 514 to 437 nm, which induces color changes from amaranth to yellow. Non-fluorescent TP1 upon interaction with CN− exhibits a ca. 17-fold fluorescence enhancement at 551 nm, resulting in strong orange emission. The sensing mechanism of TP1 recognizes CN− which undergoes a nucleophilic addition reaction. Moreover, the detection limit of the probe TP1 towards CN− is 1.4 × 10−8 M, which is far lower than the WHO guideline of 1.9 μM cyanide for drinking water. In addition, the cell imaging experiments certify that TP1 can be successfully applied as a bioimaging agent for monitoring CN− in pheochromocytoma cell (PC12). Graphical abstract Image 1 Highlights • Probe TP1 with D-π-A featured structure for CN− was developed. • TP1 can detect cyanide with high sensitivity and selectivity. • The detection limit of TP1 towards CN− was 1.4 × 10−8 M. • TP1 can be applied in cell imaging with turn-on emission and low cytotoxicity. [ABSTRACT FROM AUTHOR]

An expedient and practical route for realizing a novel, substrate‐controlled diastereoselective switch strategy has been successfully developed. The [4+1] annulation of thioamides with sulfur ylides proceeded smoothly via a Michael addition triggered sequential process, and trans‐dihydrothieno[3,4‐c]coumarins were obtained because of steric hindrance effects between the benzoyl group and the unit of 2H‐chromen‐2‐one as shown in the Newman projection. Nucleophilic substitution was observed as the key step when the sulfur ylides were replaced with acetophenones in the [4+1] annulation, and a double π,π‐stacking donor‐acceptor interaction stabilized the transition state that led to the cis‐dihydrothieno[3,4‐c]coumarins. In addition, a facile chemoselective reaction was also investigated, providing a series of thieno[3,4‐c]coumarins. [ABSTRACT FROM AUTHOR]

Two‐dimensional (2D) black phosphorus (BP) has a unique band structure, but it suffers from low ambient stability owing to its high reactivity to oxygen. Covalent functionalization has been demonstrated to passivate the reactive BP effectively, however the reported covalent functionalization methods are quite limited to aryl diazonium and nucleophilic additions affording P−C and P−O−C single bonds, for which the retaining of one unpaired electron in the Group 15 phosphorus atom hampers the passivation effect. Now, covalent azide functionalization of BP nanosheets (BPNSs) is reported, leading to significant enhancement of the ambient stability of BP as confirmed by UV/Vis spectroscopic studies. The most stable configuration of the azide functionalized BPNSs (f‐BPNSs) is predicted by theoretical calculations, featuring the grafting of benzoic acid moiety onto BPNSs via the unprecedented P=N double bonds formed through in situ nitrene as a reactive intermediate. [ABSTRACT FROM AUTHOR]

The chemical functionalization of carbon nanotubes is often a prerequisite prior to their use in various applications. The covalent grafting of 4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolane (BPin) functional groups directly on the surface of multi‐ and single‐walled carbon nanotubes, activated by nucleophilic addition of nBuLi, was carried out. Thermogravimetric analysis (TGA) coupled with mass spectrometry, Raman spectroscopy, X‐ray photoelectron spectroscopy (XPS) and time‐of‐flight secondary ions mass spectrometry (ToF‐SIMS) confirmed the efficiency of this methodology and proved the integrity and covalent grafting of the BPin functional groups. These groups were further reacted with various nucleophiles in the presence of a copper(II) source in the conditions of the aerobic Chan–Lam–Evans coupling. The resulting materials were characterized by TGA, XPS and ToF‐SIMS. This route is efficient, reliable and among the scarce reactions that enable the direct grafting of heteroatoms at carbonaceous material surfaces. Boron on CNTs: The first direct grafting of boron‐based groups on carbon nanotubes (CNTs) through a two‐step nucleophilic addition and boronic acid pinacol ester (BPin)‐capture reaction is reported. The grafted BPin groups were afterwards replaced by different O‐ and N‐based nucleophiles through the copper‐catalyzed Chan–Lam–Evans coupling. [ABSTRACT FROM AUTHOR]

A computational study of the electrocyclic ring‐opening of 2‐substituted cyclobutenecarboxylic acids is presented. Detailed calculations suggest a model to predict whether the product of nucleophilic alkylation of a bicyclic lactone electrophile will be a cyclobutenecarboxylic acid or its dienoic acid isomer, based on the used nucleophile. Open, Sesame: A computational study of the electrocyclic ring‐opening of 2‐substituted cyclobutenecarboxylic acids is presented. Quantum chemical calculations analyse and clarify experimental evidence. [ABSTRACT FROM AUTHOR]

Graphical abstract The nucleophilic addition of a well-defined palladium(II) carbene complex to the electrophilic nitrogen atom of 2,6-dimesitylphenyldiazomethane and 2,6-dimesitylphenylazide. Abstract The reactivity of a nucleophilic palladium carbene, [{PC(sp2)P}HPd(PMe 3)] (1 , [PC(sp2)P] = bis[2-(di- iso -propylphosphino)phenyl]methylene), towards 2,6-dimesitylphenyldiazomethane ((dmp)CHN 2) and 2,6-dimesitylphenylazide ((dmp)N 3) was explored. When treated with (dmp)CHN 2 , the carbene complex was fully consumed to generate a 3-coordinate Pd(0) complex [{PC(N N CH(dmp))P}HPd(PMe 3)] (2), with a newly formed double bond between the backbone carbon and the terminal nitrogen of the diazo compound. Similar reactivity occurred between [{PC(sp2)P}HPd(PMe 3)] and (dmp)N 3 to yield [{PC(N N N(dmp))P}HPd(PMe 3)] (3); in this instance, there is an interaction between the newly formed C N moiety and the Pd(0) metal center, resulting in a 4-coordinate distorted tetrahedral complex. [ABSTRACT FROM AUTHOR]

Diazenyl 1,2,4‐triazol‐5(4H)‐thione derivatives were synthesized in good yields via Eschenmoser‐coupling reaction and nucleophilic attack between 1,4‐disubstituted thiosemicarbazides and 2,3,5,6‐tetrachloro‐1,4‐benzoquinone (p‐CHL). The structure of the synthesized compounds was confirmed by IR, NMR and mass spectral data as well as single crystal X‐ray analysis. Nucleophilic attack of 1,4‐disubstituted thiosemi‐carbazides on 2,3,5,6‐tetrachloro‐1,4‐benzoquinone (p‐CHL), afforded the formation of heterocyclic triazolethione derivatives via multistep reaction. The cyclization reaction required the presence of p‐CHL as a mediator and used to activate the C=S toward nucleophilic addition and elimination a molecule of substituted amine followed by cyclization and oxidation with p‐CHL. The products were confirmed by X‐ray analyses. [ABSTRACT FROM AUTHOR]

Summary of main observation and conclusion: Studies on the aggregation degrees of negatively charged phosphides derived from the nucleophilic P4 functionalization could help understand the pathway of phosphorus atoms degradation or aggregation. In this report, we have isolated and characterized four phosphorus cluster anions (P73–, P144–, P162–, and P264–) from the nucleophilic functionalization of P4 with 1,4‐dilithio‐1,3‐butadienes. These phosphorus clusters could be rationalized as the P‐atom‐containing products besides the main phospholyl lithium. Their structural features and 31P NMR behaviors are discussed based on single crystal X‐ray diffraction analysis and 31P{1H} COSY NMR analysis. We have isolated and characterized four phosphorus cluster anions including Li3(THF)6P7, Li4(THF)10P14, Li2(THF)6P16 and Li4(THF)13P26 from the nucleophilic functionalization of white phosphorus with 1,4‐dilithio‐1,3‐butadienes. Their structural features and NMR behaviors are discussed based on X‐ray diffraction analysis and low‐temperature 31P{1H} COSY NMR analysis. [ABSTRACT FROM AUTHOR]

Abstract In this work, a new reaction-based red to near-infrared (NIR) fluorescent turn-on probe for H 2 S was developed. This probe uses a readily prepared dicyanoisophorone as the fluorophore and a 2, 4-dinitrobenzenether with an ortho -aldehyde group as the reaction site. Upon addition of H 2 S, a fast nucleophilic addition of H 2 S to the aldehyde group and a following efficient intramolecular thiolysis of dinitrophenyl ether occurred, which leads to release the fluorophore and give a rapid NIR fluorescence turn-on response for H 2 S with a super large Stokes shift (244 nm). The fluorescence enhancement was found up to 105-fold and the detection limit was determined to be as low as 42 nM. Importantly, this probe shows high selectivity and sensitivity for H 2 S without interference from biothiols. Furthermore, NIR fluorescent imaging of exogenous and endogenous H 2 S in living cells with this probe was also successfully applied. All the results indicate that this probe is excellent and highly valuable. Graphical abstract Image 1 Highlights • A new dicyanoisophorone-based NIR fluorescent probe for H 2 S was reported. • This probe is highly selective and sensitive for H 2 S. • This probe shows a rapid NIR fluorescence turn-on response for H 2 S with a super large Stokes shift (244 nm). • This probe can be used to detect exogenous and endogenous H 2 S in living cells. [ABSTRACT FROM AUTHOR]

Abstract A simple novel dihydrophenazine-based chemosensor R has been developed for the detection of SO 3 2− in DMSO-H 2 O solution with turn-on fluorescence. Upon the addition of sulfite, the ICT (intramolecular charge transfer) system of the probe was destroyed owing to the nucleophilic addition of sulfite to the formyl group of R. Thus a charming orange-red fluorescence centered at 603 nm appeared, which is favorable for potential biosensing. The reaction mechanism was confirmed by MS and 1H NMR titration. In addition, the detection limit for sulfite was determined as low as 71.4 nM, which is superior to many reported probes. All above results promote the probe as a promising candidate in practical and biological applications. Graphical abstract Image 1 Highlights • A simple novel dihydrophenazine-based chemosensor R has been synthesized for the detection of SO 3 2−. • The probe has a charming turn-on orange-red fluorescence centered at 603 nm. • The detection limit for sulfite was determined as low as 71.4 nM. [ABSTRACT FROM AUTHOR]

1,3-Dienes are easily accessible chemicals that participate in a series of reactions acting on the carbon–carbon double bonds. Catalytic difunctionalization of 1,3-dienes provides a wide scope of functionalized chemicals. Pd(0) catalysts provide a diverse set of principles for the creation of asymmetric catalytic reactions, which are initiated with the oxidative addition and then undergo insertion reaction with one of double bonds of the 1,3-diene to become a π-allyl palladium species that is reactive toward nucleophilic attack. This review summarizes typical advances on the Pd(0)-catalyzed difunctionalization of 1,3- dienes in recent decades, particularly emphasizing the concepts that enable the switch from a racemic reaction to an enantioselective version. [ABSTRACT FROM AUTHOR]

Reaction of racemic phosphinic acid derivatives with chiral alcohols proceeds with predominant formation of one diastereomer. The highest level of enrichment has been obtained for transesterfication of racemic methyl benzylphenylphosphinate (64% de). The outcome of the reaction depends on both the structure of chiral alcohol and the starting organophosphorus compound. The results strongly suggest that the nature of the observed phenomena is not a classical equilibration of intermediates found in dynamic kinetic resolution process but is a result of a different reactivity of both enantiomers of racemic substrate towards the same chiral nucleophile. [ABSTRACT FROM AUTHOR]

Abstract Two indole organic salt derivatives 1 and 2 with two potential reactive sites for cyanide were synthesized by very simple method. The compounds exhibit highly sensitive and selective response for cyanide with obvious UV–vis absorption, color change and fluorescence quench. Color change under natural and UV light can be observed easily by naked eyes. Their absorption responses for cyanide are markedly different from the corresponding normal cyanide chemosensors because of N H*CN− intermolecular hydrogen-bond interaction. The difference of absorption spectra between these compounds and the corresponding normal cyanide chemosensors were compared. Their recognition mechanisms for cyanide anions were analyzed by in situ 1H NMR and Job's plots. The analysis indicates that cyanide anions are bonded to C C bonds in conjugated bridge of the compounds. At the same time, N H*CN− intermolecular hydrogen-bond interaction is accompanied. These chemosensors have been successfully applied for determination of CN− in living cells. Graphical abstract Image 1 Highlights • Two indole derivatives with two reactive sites for cyanide detection were developed. • The compounds can recognize CN− with obvious spectra and color change. • CN− is bonded to C C bond in conjugated bridge of the compounds. • The chemosensors were successfully applied for determination of CN− in living cells. • Intermolecular hydrogen-bond interaction may also occur and plays an important role. [ABSTRACT FROM AUTHOR]

Abstract Targeted covalent inhibitors have become an integral part of a number of therapeutic protocols and are the subject of intense research. The mechanism of action of these compounds involves the formation of a covalent bond with protein nucleophiles, mostly cysteines. Given the abundance of cysteines in the proteome, the specificity of the covalent inhibitors is of utmost importance and requires careful optimization of the applied warheads. In most of the cysteine targeting covalent inhibitor programs the design strategy involves incorporating Michael acceptors into a ligand that is already known to bind non-covalently. In contrast, we suggest that the reactive warhead itself should be tailored to the reactivity of the specific cysteine being targeted, and we describe a strategy to achieve this goal. Here, we have extended and systematically explored the available organic chemistry toolbox and characterized a large number of warheads representing different chemistries. We demonstrate that in addition to the common Michael addition, there are other nucleophilic addition, addition-elimination, nucleophilic substitution and oxidation reactions suitable for specific covalent protein modification. Importantly, we reveal that warheads for these chemistries impact the reactivity and specificity of covalent fragments at both protein and proteome levels. By integrating surrogate reactivity and selectivity models and subsequent protein assays, we define a road map to help enable new or largely unexplored covalent chemistries for the optimization of cysteine targeting inhibitors. Graphical abstract Image 1 Highlights • A broad library of cysteine targeting warheads was explored and characterized. • Diverse chemical reactions are suitable for specific covalent protein modification. • Warheads impact the reactivity and specificity of covalent fragments. • A road map for the optimization of cysteine targeting inhibitors is proposed. [ABSTRACT FROM AUTHOR]

A set of novel aromatic and heteroaromatic bench‐stable sulfoxide‐based boronates was prepared. The structure of the boronates was established by means of X‐ray crystallography, and the prepared boronates were successively used in Suzuki cross‐coupling reactions under different conditions. We also developed a tandem Suzuki reaction so that a base is generated during the nucleophilic addition of Grignard reagents to 4‐bromobenzaldehyde. The formed intermediates were smoothly coupled with the prepared boronates and the boronic acids under external base‐free conditions. [ABSTRACT FROM AUTHOR]

An efficient protocol for the construction of 3‐carbonyl functionalized 4‐pyrones has been developed using a transition‐metal free thermal cascade reaction of diazodicarbonyls with β‐enamino esters or β‐enamino ketones. This reaction proceeds via cascade carbene generation, ketene formation via thermal Wolff‐rearrangement, nucleophilic addition, intramolecular cyclization, and elimination. This protocol provides a rapid synthetic route to diverse 2,3,5‐trisubstituted 4‐pyrone derivatives. [ABSTRACT FROM AUTHOR]

Alkylnitrilium derivatives of nido-carborane 10-RC≡N-7,8-C2B9H11 (R = Me, Et) have been prepared by the reaction of the parent anion [7,8-C2B9H12]− with mercury(ii) chloride in mixtures of the corresponding nitriles and benzene. Hydrolysis of 10-EtC≡N-7,8-C2B9H11 resulted in iminol 10-EtC(OH)=HN-7,8-C2B9H11 which on treatment with a base gave the corresponding amide 10-EtC(=O)HN-7,8-C2B9H11. The reactions of 10-EtC≡N-7,8-C2B9H11 with alcohols and thiols were found to give stable imidates and thioimidates 10-EtC(XR)=HN-7,8-C2B9H11 (X = O, R = Me, Et, iPr, Bu; X = S, R = Et, Bu, Hx) as mixtures of E- and Z-isomers that were successfully separated by column chromatography. The crystal molecular structures of E-10-EtC(OR)=HN-7,8-C2B9H11 (R = Et, i-Pr, Bu) and Z-10-EtC(SEt)=HN-7,8-C2B9H11 were determined by single crystal X-ray diffraction. [ABSTRACT FROM AUTHOR]

Alkylnitrilium derivatives of nido-carborane 10-RC≡N-7,8-C2B9H11 (R = Me, Et) have been prepared by the reaction of the parent anion [7,8-C2B9H12]− with mercury(ii) chloride in mixtures of the corresponding nitriles and benzene. Hydrolysis of 10-EtC≡N-7,8-C2B9H11 resulted in iminol 10-EtC(OH)=HN-7,8-C2B9H11 which on treatment with a base gave the corresponding amide 10-EtC(=O)HN-7,8-C2B9H11. The reactions of 10-EtC≡N-7,8-C2B9H11 with alcohols and thiols were found to give stable imidates and thioimidates 10-EtC(XR)=HN-7,8-C2B9H11 (X = O, R = Me, Et, iPr, Bu; X = S, R = Et, Bu, Hx) as mixtures of E- and Z-isomers that were successfully separated by column chromatography. The crystal molecular structures of E-10-EtC(OR)=HN-7,8-C2B9H11 (R = Et, i-Pr, Bu) and Z-10-EtC(SEt)=HN-7,8-C2B9H11 were determined by single crystal X-ray diffraction. [ABSTRACT FROM AUTHOR]

The N‐iodosuccinimide‐mediated spirocyclization of tryptamine‐derived isocyanides to generate spiroindolenines is reported. The products contain both an imine and an imidoyl iodide as flexible handles for follow‐up chemistry. Nucleophilic addition typically occurs chemoselectively on the imine moiety with complete diastereoselectivity, providing opportunities for the construction of complex molecular frameworks. The synthetic potential of the method was showcased in the formal total synthesis of (±)‐aspidofractinine. [ABSTRACT FROM AUTHOR]

Halogen atoms in molecular crystals may be involved in various interactions, often playing a very important role in structure stabilization. By introducing electron-donating groups, such as NH2, the electron density of the molecule is changed and thus interactions with the bromine substituent may alter. Herein, the crystal structures of meta-bromonitrobenzene and its NH2-substituted derivatives are analyzed. In all four described structures, namely m-bromonitrobenzene [Charlton & Trotter (1963). Acta Cryst. 16, 313], 4-bromo-2-nitroaniline (C6H5BrN2O2, 1), 2-bromo-6-nitroaniline (2) and 2-bromo-4-nitroaniline [Arshad et al. (2009). Acta Cryst. E65, o480], the Br atom is engaged in different interactions (Br…л, Br…O, Br…Br and C--H…Br, respectively). The Hirshfeld surface analysis (HS) and Reduced Density Gradient NonCovalent Interaction (RDG NCI) plots are used to prove the relevance, directionality and stabilizing nature of these interactions. Their modifications have been associated with the position of the amino group in the molecular structure and its influence on charge distribution analyzed with electrostatic potential surfaces (EPS). The diversification of the interactions has been correlated with a σ-hole potential value that enables a switching of the Bratom character from electrophilic to nucleophilic. [ABSTRACT FROM AUTHOR]

A novel retro-ene reaction via a [4.4.3]propellane intermediate containing a quaternary ammonium linkage was developed. The feature of this acetic anhydride mediated rearrangement includes the elimination of an acetoxy group at the C14 position and subsequent intramolecular nucleophilic addition of a nitrogen functional group to form an isolable ammonium salt intermediate. We clarified the reaction mechanism utilizing the deuterated derivative. [ABSTRACT FROM AUTHOR]

Traditional strategies for the functionalization of materials displaying hydroxyl groups either require active esterification reagents or involve the nucleophilic attack of the hydroxyl group toward electrophilic groups. The former tends to hydrolyze in aqueous solutions while the latter occurs under harsh conditions. Herein, the authors reported a new method for the functionalization of hydroxyl groups on the surface via catalytic oxa-Michael addition with vinyl sulfones. Using hydroxyl group terminated self-assembled monolayers as a model surface, a series of organocatalysts were screened and triphenylphosphine stood out for the best catalytic activity. The catalytic reaction on the surface was characterized by x-ray photoelectron spectroscopy. The information of reaction kinetics was obtained using static water contact angle measurements. Once conjugated with ligands onto the functionalized surfaces, the multivalence binding of proteins was investigated by quartz crystal microbalance experiments. By varying the reaction conditions, e.g., catalyst types and reaction times, ligands can be anchored with a controllable density, which would be helpful to establish the relationships between ligand density and bioactivity. [ABSTRACT FROM AUTHOR]

Reported is a novel two‐step ring‐expansion strategy for expeditious synthesis of all ring sizes of synthetically challenging (hetero)aryl‐fused medium‐sized lactams from readily available 5–8‐membered cyclic ketones. This step‐economic approach features a remote radical (hetero)aryl migration from C to N under visible‐light conditions. Broad substrate scope, good functional‐group tolerance, high efficiency, and mild reaction conditions make this procedure very attractive. In addition, this method also provides expedient access to 13–15‐membered macrolactams upon an additional one‐step manipulation. Mechanistic studies indicate that the reaction involves an amidyl radical and is promoted by acid. [ABSTRACT FROM AUTHOR]

Abstract An efficient synthetic methodology for the preparation of phosphorus substituted bis-(3-indolyl)methane through a double nucleophilic addition of indole derivatives to an in situ generated α-iminophosphonate is reported. In addition, bis-(3-indolyl)methane substrates showed in vitro cytotoxicity, inhibiting the growth of carcinoma human tumor cell lines A549 (carcinomic human alveolar basal epithelial cell) and SKOV03 (human ovarian carcinoma). Graphical abstract Image 1 Highlights • An efficient synthesis of bis(3-indolyl)methane derivatives is reported. • Phosphorated bis-(3-indolyl)methane derivatives are hybrid substrates. They showed in vitro cytotoxicity against cancer. • Substrates 13j and 12c derived from 5-methylindole show very good IC 50 values of about 0.06 μM. [ABSTRACT FROM AUTHOR]

A variety of 3‐substituted‐6,8‐dimethylchromones have been synthesized and characterized. The chemical reactivity of 3‐substituted‐6,8‐dimethylchromones was studied towards some nucleophiles, namely, S‐benzyldithiocarbazate, o‐phenylenediamine, and cyanoacetamide, and a diversity of products were efficiently synthesized. Reactions of 3‐substituted‐6,8‐dimethylchromones (except 3‐formyl‐6,8‐dimethylchromone), with nucleophilic reagents, usually proceed through nucleophilic attack at C‐2 position followed by different types of heterocyclization depending on the functional group present at C‐3 position. Structures of the newly synthesized products have been established based on elemental analysis and spectral data. [ABSTRACT FROM AUTHOR]

Abstract: A convenient synthesis of dicyanophosphide and dicyanoarsenide anions is reported. These heavy homologues of the long‐known and fundamentally important dicyanamide anion were formed through the nucleophilic displacement of bis(diphenylphosphino)ethane (dppe) from the pnictogen+ transfer agents [dppePn][BPh4] (Pn=P, As) by exposure to cyanide salts. The protocol requires three synthetic steps from commercially available materials and the [dppePn][BPh4] salts are remarkably temperature, air, and moisture stable. All products have been fully characterized by spectroscopic methods and by single‐crystal X‐ray diffraction, and the electronic structures of the DCPn anions have been assessed computationally. [ABSTRACT FROM AUTHOR]

An efficient metal-free approach for the synthesis of N-coumaryl amino acids and the first one-step synthesis of 4-hydrazinocoumarin from 4-hydroxycoumarin was developed. The nucleophilic addition of amino acid methyl esters to 4-tosylcoumarins produced a series of 4-N-α-coumaryl amino acids in good to excellent yields without racemization. The antioxidant activities of the synthesized compounds were investigated using DPPH and FRAP methods. 4-Hydrazinocoumarin and N-coumaryl tyrosine had the best antioxidant activity. The antimicrobial activities of the compounds against Gram-positive was stronger than Gram-negative. 4-Hydrazinocoumarin showed the best antibacterial effect. [ABSTRACT FROM AUTHOR]

Abstract: We report the first total synthesis of (−)‐17‐nor‐excelsinidine, a zwitterionic monoterpene indole alkaloid that displays an unusual N4−C16 connection. Inspired by the postulated biosynthesis, we explored an oxidative coupling approach from the geissoschizine framework to forge the key ammonium–acetate connection. Two strategies allowed us to achieve this goal, namely an intramolecular nucleophilic substitution on a 16‐chlorolactam with the N4 nitrogen atom or a direct I2‐mediated N4−C16 oxidative coupling from the enolate of geissoschizine. [ABSTRACT FROM AUTHOR]

Organomagnesium reagents are among the most important reagents in organic chemistry because of their great utility in forming carbon–carbon bonds. Although most enantioselective reactions using these organometallics involve transmetalation, the past decade has witnessed impressive advances in direct chiral-ligand-mediated reactions of organomagnesiums. This short review presents an overview of these achievements in enantioselective nucleophilic additions and substitutions. 1 Introduction 2 Enantioselective Nucleophilic Additions 2.1 Addition to C=O Bonds 2.2 Addition to C=N Bonds 2.3 Addition to C=C Bonds 3 Enantioselective Substitution Reactions 3.1 Sulfoxide–Magnesium Exchange 3.2 Desymmetrization via Anhydride Opening 3.3 Asymmetric Allylic Alkylation (AAA) 4 Conclusion. [ABSTRACT FROM AUTHOR]

An organobase-directed, regiodivergent 1,3-dipolar cycloaddition of azomethine ylides and 2-hydoxybenzylidene indandiones is reported. The scarcely explored reversal of the nucleophilic site in azomethine ylides has been exploited for their regiodivergent (3+2) cycloaddition, which subsequently resulted in two different cascade processes to generate functionally distinct chromenopyrrolidines in a diversity oriented manner. [ABSTRACT FROM AUTHOR]

Abstract: The first example of the synthesis of mono‐N,O‐B‐chelated dipyrromethene (BODIPY) derivatives through an unexpected intramolecular nucleophilic displacement of the fluorine by alkenols in the presence of boron trifluoride as Lewis acid is reported. The chlorine in the indacene core allowed for further structural modifications through nucleophilic substitutions or palladium‐catalysed coupling reactions to afford new fluorophores with tuneable photophysical properties. Their expanded conjugation structure resulted in distinct red‐shifted absorption and emission spectra in organic solutions. Furthermore, the twisted steric hindrance of the benzene substitution patterns suppressed aggregation‐induced quenching, leading to an enhanced NIR emission in the aggregate/solid state, which was rarely observed for BODIPY dyes. Nanoparticles of the fluorophores formed by the assembly with the polymeric surfactant F127 were successfully used for bioimaging of living cells and for tumour‐targeted imaging in a tumour‐bearing mouse model. [ABSTRACT FROM AUTHOR]

A diastereoselective nucleophilic dichloromethylation between the N - tert -butanesulfinyl imines and dichloromethyllithium was developed. A series of 2-chloroaziridines with excellent yields and dr values were obtained via this nucleophilic addition and N -alkylation in one pot. On the basis of X-ray crystallography experiment, the predicting model for this diastereoselective transformation was provided. [ABSTRACT FROM AUTHOR]

Aldehydes are relevant analytes in a wide range of samples, in particular, food and beverages but also body fluids. Hydrazines can undergo nucleophilic addition with aldehydes or ketones giving origin to hydrazones (a group of stable imines) that can be suitably used in the identification of aldehydes. Herein, 4-hydrazinobenzoic acid (HBA) was, for the first time, used as the derivatizing agent in analytical methodologies using liquid chromatography aiming the determination of low-molecular aldehydes. The derivatization reaction was simultaneously performed along with the extraction process, using gas-diffusion microextraction (GDME), which resulted in a clean extract containing the HBA-aldehyde derivates. The corresponding formed imines were determined by both high-performance liquid chromatography (LC) with UV spectrophotometric detection (HPLC-UV) and capillary electrophoresis with diode array detection (CE-DAD). HBA showed to be a rather advantageous derivatization reagent due to its stability, relatively high solubility in water and other solvents, high selectivity and sensibility, reduced impurities, simple preparation steps and applicability to different separation and/or different detection techniques. Limits of detections (LODs) of the optimized methodologies (in terms of time and pH among other experimental variables) were all below 0.5 mg L −1 , using both instrumental techniques. Furthermore, for the first time, the HBA-aldehyde derivatives were analyzed by LC with mass spectrometry (LC-MS), demonstrating the possibility of identification by MS of each compound. The developed methodologies were also successfully applied in the analysis of formaldehyde and acetaldehyde in several alcoholic beverages. This was also the first time GDME was combined with CE, showing that it can be a valuable sample preparation tool for electrophoresis, in particular by eliminating the interference of ions and inorganic constituents present in the samples. [ABSTRACT FROM AUTHOR]

The nucleophilic addition of 2-pyridyl carbamidoxime to the C≡N group of the aliphatic nitrilium closo -decaborate clusters (PhCH 2 PPh 3 )[B 10 H 9 NCR] (R = Me, Et, and i Pr) proceeds to give 2-iminium closo -decaborates (68–88% isolated yields). A systematic kinetic and theoretical study of the nucleophilic addition indicates that the reactivity of the nitrile ligand at the boron cluster unexpectedly increases in the order of R: Me < Et <  i Pr. It was shown theoretically, that the electrophilicity of the C≡N group is primarily determined by hyperconjugation with the neighboring aliphatic moiety, which induced by substantial (ca. +0.6 e ) positive charge at the nitrile C atom. [ABSTRACT FROM AUTHOR]

A novel organozincate of RMgX ⋅MeZnOMe ⋅LiCl type, formed in situ via transmetalation of Grignard reagent RMgBr ⋅LiCl with MeZnOMe, is shown to be an excellent organometallic species in the nucleophilic addition/Oppenauer oxidation of aldehydes to generate aromatic ketones in high yield. This transformation allows quick access to structurally diverse aryl, heteroaryl, benzyl and alkyl ketones with broad substrate scope and excellent functional group tolerance. [ABSTRACT FROM AUTHOR]