Synthesis of a Thiazole Library via an Iridium-Catalyzed Sulfur Ylide Insertion Reaction

Divergent Construction of α,α-Difunctionalized Ketones via [1,2]-Sigmatropic Rearrangement/Alkylation-Hydroxylation/Dialkylation of I(III)/S(VI) Ylides

The rare [1,2]-sigmatropic rearrangement of sulfoxonium-iodonium hybrid ylides is described, which enables the efficient sulfoxidation/sulfonylation-alkylation of I(III)/S(VI) ylides with 1,3-dicarbonyls. By slight modification of the reaction conditions, controllable alkylation-hydroxylation and dialkylation of I(III)/S(VI) ylides were achieved. This strategy affords a diverse array of α,α-difunctionalized ketones in moderate to good yields, demonstrating broad substrate scope. These findings provide an important advancement in the [1,2]-sigmatropic rearrangement of sulfoxonium ylides and highlight the divergent reactivity of I(III)/S(VI) ylides.

Palladium-Catalyzed α-Arylation of Sulfoxonium Ylides with Aryl Thianthrenium Salts via C-S and C-H Bond Activation

Diverse α-aryl α-carbonyl sulfoxonium ylides were efficiently synthesized in yields ranging from moderate to high via a palladium-catalyzed α-arylation of sulfoxonium ylides with aryl thianthrenium salts. The reactions proceeded smoothly via C-S and C-H bond functionalization, exhibiting broad substrate scope and good compatibility to various functionalities. In addition, the scale-up synthesis could be achieved, and the one-pot protocol commencing from the use of simple arene as the precursor of aryl thianthrenium salt could also be accomplished.

Palladium-catalyzed α-arylation of sulfoxonium ylides with aryl fluorosulfates

A variety of α-arylated sulfoxonium ylides could be facilely synthesized in modest to high yields through α-arylation of sulfoxonium ylides with aryl fluorosulfates via C-O bond functionalization under palladium catalysis. Reactions using readily available and bench-stable aryl fluorosulfates as effective and appealing arylating agents showed both good substrate scope and broad functionality tolerance. Important functional groups such as nitro, cyano, formyl, acetyl, methoxycarbonyl, trifluoromethoxy, fluoro, and chloro embedded in substrates remained intact during the course of the reaction, and could be subjected to downstream modification. In addition, the reaction could be readily scalable and applied in the late-stage modification of complex molecules.

Recent Advances in Design, Synthesis, and Biological Activity Studies of 1,3-Selenazoles

The review examines recent advances in the design and synthesis of 1,3-selenazole derivatives since 2000. Various synthetic approaches to 1,3-selenazoles and reaction conditions are discussed. The beneficial properties of 1,3-selenazoles, especially their biological activity, are emphasized. Compounds with antitumor, antiviral (HIV-1 and HIV-2), antibacterial, antifungal, antiproliferative, anticonvulsant, and antioxidant activity are highlighted.

Brønsted acid-mediated thiazole synthesis from sulfoxonium ylides

A Brønsted acid-mediated insertion of thioureas/thioamides into sulfoxonium ylides to synthesise 40 thiazoles (34-95% yields) under mild, metal-free conditions is described. This process is scalable, substrate-tolerant (including both α-substituted and heterocyclic ylides/groups) and was successfully applied to the late-stage functionalisation of the complex chemical probe molecule (+)-JQ1.

Substrate-dependent regiodivergence in [3 + 2] annulation reactions of 2-(phenacylethylidene)cyclobutanones with thioureas

The [3 + 2] annulation reaction between a thiourea, an ambident dinucleophile, and a 2-(phenacylethylidene)cyclobutanone, containing a novel pull-pull alkene system, could in principle proceed with several chemo- and regioselectivity profiles. Here we describe a convenient synthesis of the functionalized cyclobutanone substrates and show that they react with thioureas in a manner that is rationalized mechanistically in terms of the steric and electronic effects at play. The [3 + 2] annulation proceeds in mild, additive-free conditions to provide access to previously unknown cyclobutane-fused imidazolidine-2-thione and thiazolidine-2-imine derivatives in good yields.

Synthesis of N-Aryl-4-trifluoromethylthiazol-2-amines via Insertion/Annulation of Trifluoromethylimidoyl Sulfoxonium Ylides with Sodium Thiocyanate

An efficient p-TsOH-mediated insertion of sodium thiocyanate into trifluoromethylimidoyl sulfoxonium ylides has been reported, affording annulated N-aryl-4-trifluoromethylthiazol-2-amines in 42-84% yields in a one-pot manner. This protocol encompasses a variety of trifluoromethylimidoyl sulfoxonium ylides with thiocyanate serving as the source of the "S-C═N" moiety of the thiazole ring. The versatile transformations of the resulting pharmacologically important N-aryl-4-trifluoromethylthiazol-2-amines were also demonstrated.

Isocyanide-Based Multicomponent Reaction: Cascade α-Acyloxylation/Carboxamidation and [3 + 1+1] Cyclization of I(III)/S(VI)-Ylides

A metal-free cascade of α-acyloxylation/carboxamidation of I(III)/S(VI)-ylides, carboxylic acids, and isonitriles via a Passerini-like multicomponent reaction is reported. Unexpectedly, [3 + 1+1] cyclization involving I(III)/S(VI)-ylides and two molecules of ethyl isocyanoacetate was observed. The strategy allows for the synthesis of unsymmetrical α,α-disubstituted ketones and functionalized pyrroles with up to 99% yield and wide substrate compatibility. Notably, the procedure has been extended to the late-stage modification of drugs and natural products, offering an elegant complement to the classic Passerini reaction.

A Platform for the Synthesis of Diverse Phosphonyl and Thiofunctionalized Sulfoxonium Ylides

A practical strategy for the construction of diverse phosphonyl and thiofunctionalized sulfoxonium ylides via controllable monofunctionalization of hybrid I(III)/S(VI) ylides is presented. This process allows efficient P-H insertion of I(III)/S(VI) ylides under Cu catalysis, enabling the synthesis of phosphonyl sulfoxonium ylides, whereas reaction with sulfur-containing reagents including AgSCF3, KSC(S)OR, and KSCN under mild conditions resulted in α-trifluoromethylthiolation, dithiocarbanation, and thiocyanation of sulfoxonium ylides accordingly. Of note, wide substrate compatibility (108 examples), excellent efficiency (up to 99% yield), gram-scale experiments, and various product derivatizations highlight the synthetic utility of this protocol.

Electrochemical Enaminone-Thioamide Annulation and Thioamide Dimeric Annulation for the Tunable Synthesis of Thiazoles and 1,2,4-Thiadiazole

A green and sustainable electrochemical oxidative cyclization of enaminones with thioamides under metal- and oxidant-free conditions has been developed, providing an efficient approach for thiazole synthesis. Furthermore, 1,2,4-thiadiazoles can be selectively accessed via the electrochemical dimerization of thioamides in the absence of enaminones.

Straightforward access to α-thiocyanoketones and thiazoles from sulfoxonium ylides

Efficient, versatile, and metal-free strategies for synthesizing α-thiocyanoketones and thiazoles from β-ketosulfoxonium ylides and ammonium thiocyanate have been described. Due to its simplicity, benign reaction conditions, excellent chemoselectivity, and high yield, this method represents a unique approach for divergent synthesis. Finally, the potential value of the developed methods is demonstrated via large-scale reactions and synthesis of Fanetizole, an anti-inflammatory drug.

Divergent Synthesis of Tetrasubstituted Phenols via [3 + 3] Cycloaddition Reaction of Vinyl Sulfoxonnium Ylides with Cyclopropenones

Two categories of tetrasubstituted phenols were prepared via the cycloaddition reaction of vinyl sulfoxonnium ylides with cyclopropenones in a switchable manner. Copper carbenoid was proposed as the active intermediate in the process of 2,3,4,5-tetrasubstituted phenols formation, while 2,3,5,6-tetrasubstituted phenols were generated via the direct [3 + 3] annulation of vinyl sulfoxonnium ylides with cyclopropenones under metal-free conditions. Further synthetic applications were also demonstrated.