Facile synthesis of quinoxaline-2-thiol and quinoxaline from α-oxo sulfines and o-aryl diamines

A series of quinoxaline-2-thiol and quinoxaline were prepared in moderate to good yields from various phenacyl sulfoxides bearing 1-methyl-1H-tetrazole and o-aryl diamines. The proposed reaction mechanism involves generation of sulfines from the phenacyl sulfoxides bearing 1-methyl-1H-tetrazole through thermolysis elimination. Then, site-selectively carbophilic addition of sulfines by o-aryl diamines, followed by elimination, intramolecular nucleophilic addition and dehydration condensation. The current method provides a direct and simple strategy for the preparation of quinoxaline-2-thiols and quinoxalines.

Theoretical investigation of the mechanism of DMAP-promoted [4 + 2]-annulation of prop-2-ynylsulfonium with isatoic anhydride

The mechanism for DMAP-promoted [4 + 2]-annulation of prop-2-ynylsulfonium with isatoic anhydride is investigated using the M06-2X functional. The reaction comprises isomerization of prop-2-ynylsulfonium in stage 1. Stage 2 includes DMAP-promoted deprotonation, nucleophilic addition, ring opening, and decarboxylation. Three steps of intramolecular cycloaddition, DMAP-promoted protonation, and dealkylation occur in stage 3, generating methylated DMAP and neutral thioether, which undergo double-bond isomerization to yield 3-methylthio-4-quinolone. The ability of DMAP to promote the reaction lies in the barrier decrease for alkyne isomerization, deprotonation/protonation of allenes, and dealkylation as effective bases for transferring protons and methyl groups. The roles of prop-2-ynylsulfonium and isatoic anhydride were demonstrated to be C2 and C4 synthons via Multiwfn analysis on the frontier molecular orbital. An alternative path was also confirmed by the Mayer bond order of the vital transition states.

Design, synthesis and evaluation of structurally diverse ortho-acylphenol-diindolylmethane hybrids as anticancer agents

A highly efficient synthesis of structurally diverse ortho-acylphenol–diindolylmethane hybrids 3 using carboxylic acid-activated chromones as versatile synthetic building blocks is reported here for the first time, through 1,4-nucleophilic addition and followed by a decarboxylation and pyrone ring opening reaction process.

An umpolung strategy for rapid access to thermally activated delayed fluorescent (TADF) materials based on phenazine

Herein, Ag(I)-promoted regioselective intramolecular radical nucleophilic addition/rearrangement of 2-aryl diazaboroles have been accomplished for the first time to construct phenazine structures. This protocol is an umpolung strategy based on classical...

Copper-Catalyzed Ring-Opening Reactions of Alkyl Aziridines with B2pin2: Experimental and Computational Studies

The possibility to form new C–B bonds with aziridines using diboron derivatives continues to be a particularly challenging field in view of the direct preparation of functionalized β-aminoboronates, which are important compounds in drug discovery, being a bioisostere of β-aminoacids. We now report experimental and computational data that allows the individuation of the structural requisites and of reaction conditions necessary to open alkyl aziridines using bis(pinacolate)diboron (B2pin2) in a regioselective nucleophilic addition reaction under copper catalysis.

Synthesis and Antimalarial Activity of 7-Chloro-4-(4-(2-(Oxo, Hydroxyl & Fluoro-2-1 (4-Phenyl)Ethyl)Piperazin-1-yl)Quinoline Derivatives

Since these days, microbes are resistant to the drugs available in the market, which has caused an alarming impact on society. 18 compounds in a series of 7-chloro-4-(piperazin-1-yl)quinoline derivatives were synthesized by nucleophilic addition reaction of piperazine with 4,7-dichloroquinoline followed by phenacyl bromides addition to heteroaryl piperazine and then reduction and fluorination. All 18 compounds were evaluated in vitro for their antimalarial activity against plasmodium falciparum strain. Although 12 compounds showed good activity, compound 3c was found to be more potent than standard drug Quinine having MIC 0.18 μg/ mL. On the other hand, 3d, 3e, 5a, and 5f were found to be equipotent (MIC 0.26 μg/ mL) to the standard drug.

Cobalt-Catalyzed Cyclization of 2-Bromobenzamides with Carbodiimides: A New Route for the Synthesis of 3-(Imino)isoindolin-1-ones

A novel synthetic pathway to approach 3-(imino)isoindolin-1-ones by the Co-catalyzed cyclization reaction of 2-bromobenzamides with carbodiimides has been developed. This catalytic reaction can tolerate a variety of substituents and provide corresponding products in moderate yields for most cases. According to the literature, the reaction mechanism is proposed through the formation of a five-membered aza-cobalacycle complex, which carries out the following reaction subsequence, including nucleophilic addition and substitution, to furnish the desired structures.

Addition Coupled Electron Transfer (ACET) and Addition Coupled Electron Coupled Proton Transfer (ACPCET)

The new types of elementary reaction in which a nucleophilic addition (A) to quinones is coupled with electron transfer (ET) and even further proton transfer (PT) are suggested herein by density functional theory calculation, which are called Addition Coupled Electron Transfer (ACET) or Addition Coupled Electron Coupled Proton Transfer (ACPCET). With a [2.2]paracyclophane-derived biquinone (1) as the substrate, the nature of nucleophilic addition onto its sp2 carbons exhibits a change from stepwise A-ET-PT to ACET-PT and further to ACPCET, in parallel with the decreased nucleophilicity of the attacking reagent. In addition, we further proposed six possible potential energy surfaces and the coupling modes between A, ET and PT, in which three have been found in this work. Quasi-classical trajectory shows that the ACET and PT event can also be dynamically concerted even for an ACET-PT mechanism.