CS2/KOH System-Promoted Stereoselective Synthesis of (E)-Alkenes from Diarylalkynes and a "Hidden" Zinin-Type Reduction of Nitroarenes into Arylamines.

In this work, we present the CS2/KOH system as a practical and efficient reductive medium for obtaining (E)-alkenes from alkynes through a highly stereoselective semireduction reaction. This cost-effective system enabled successful semireduction reactions of diverse alkynes using water as a hydrogen source, yielding moderate to excellent yields. The versatility of this protocol is further demonstrated through the synthesis of relevant compounds such as pinosylvin and resveratrol precursors, along with the notable anticancer agent DMU-212. Furthermore, during the reaction scope investigation, we serendipitously disclosed that this reductive system was also able to promote a Zinin-type reaction to reduce nitroarenes into arylamines.

Palladium-Catalyzed Direct Selanylation of Chalcogenophenes and Arenes Assisted by 2-(Methylthio)amide.

The direct and selective conversion of a C-H bond into a C-Se bond remains a significant challenge, which is even more intricate with substrates having an innate regioselectivity under several reaction conditions, such as chalcogenophenes. We overrode their selectivity toward selanylation using palladium, copper, and the 2-(methylthio)amide directing group. This chelation-assisted direct selanylation was also suitable for mono and double ortho functionalization of arenes. The mechanistic studies indicate high-valent Pd(IV) species in the catalytic cycle, a reversible C-H activation step, and Cu(II) as a sequestering agent for organoselenide byproducts.

Transition metal catalysed direct sulfanylation of unreactive C-H bonds: an overview of the last two decades.

Transition metal catalysed direct sulfanylations of unreactive C-H bonds have become a unique and straightforward synthetic strategy in late-stage C-S bond formation of relevant complex molecules. Such transformations represent a breakthrough in modern synthetic organic chemistry, as they offer unusual reactivity patterns and avoid pre-functionalization of the starting materials. Despite inherent challenges in activating/functionalizing unreactive C-H bonds, a considerable number of different transition metals have shown the ability to selectively catalyze these processes toward C-S bond formation. In this sense, this review article covers the development and mechanistic analysis of the direct sulfanylation of Csp3-H and Csp2-H bonds through transition metal catalysed reactions in the last two decades, providing an essential guide for organic chemists working on this research area.

Trithiocarbonate Anion as a Sulfur Source for the Synthesis of 2,5-Disubstituted Thiophenes and 2-Substituted Benzo[b]thiophenes.

The trithiocarbonate anion (CS32-) was generated in situ from CS2 and KOH in dimethyl sulfoxide by a simple method and used as a novel synthetic equivalent of the S2- synthon for the synthesis of 2,5-disubstituted thiophenes from 1,3-butadiynes. Additionally, this system was employed for the metal-free synthesis of 2-substituted benzo[b]thiophenes from 2-haloalkynyl (hetero)arenes. These compounds were obtained from a cheap and readily available sulfur source in moderate to good yields, with good functional group tolerance.