A Convenient One-Pot Synthesis of Thiol Esters from Disulfides using a Zn/AlCl3 system

Cu-Catalyzed Oxidative Thioesterification of Aroylhydrazides with Disulfides

An alternative thioesterification reaction via copper-catalyzed oxidative coupling of readily available aroylhydrazides with disulfides is developed, in which oxidative expulsion of N₂ overcomes the activation barrier between the carboxylic acid derivatives and the products. The reaction produces various thioesters in good to excellent yields with good functional group tolerance. In the reaction, stable and easily available aroylhydrazides are used as acyl sources and the relatively odorless disulfides are used as S sources. Mechanistic investigations demonstrate that the reaction of copper salt and oxidant (NH₄)₂S₂O₈ allows for achievement of tandem processes, including deprotonation, free-radical-mediated denitrogenation, and C-S bond formation.

A Simple Zinc-Mediated Method for Selenium Addition to Michael Acceptors

In this work, we focused our attention on seleno-Michael type reactions. These were performed using zinc-selenolates generated in situ from diphenyl diselenide 1, 1,2-bis(3-phenylpropyl)diselenide 30, and protected selenocystine 31 via an efficient biphasic Zn/HCl-based reducing system. Alkenes with a variety of electron-withdrawing groups were investigated in order to gauge the scope and limitations of the process. Results demonstrated that the addition to acyclic α,β-unsaturated ketones, aldehydes, esters amides, and acids was effectively achieved and that alkyl substituents at the reactive β-centre can be accommodated. Similarly, cyclic enones undergo efficient Se-addition and the corresponding adducts were isolated in moderate to good yield. Vinyl sulfones, α,β-unsaturated nitriles, and chalcones are not compatible with these reaction conditions. A recycling experiment demonstrated that the unreacted Zn/HCl reducing system can be effectively reused for seven reaction cycles (91% conversion yield at the 7° recycling rounds).

KF/Al2O3 catalysed synthesis of thiol esters from N-acylphthalimides and thiols

A new method for the preparation of thiol esters from N-acylphthalimides and thiols in the presence of KF/Al2O3 is introduced.

Reduction cleavage of S–S bond by Zn/Cp2TiCl2: Application for the synthesis of β-arylthiocarbonyl compounds

Diaryl disulfides were reduced efficiently by a Zn/Cp2TiCl2 system at room temperature in dry THF to give the corresponding nucleophilic sulfur anion–titanocene complex, followed by reaction with α, β-unsaturated esters (ketones or nitriles) to afford the corresponding β-arylthioesters(ketone or nitrile) in good yields.

Synthesis of Allylic Sulfides via Cleavage of S–S Bonds Promoted by Zinc Metal in DMF

Cleavage of S–S bonds was achieved without any activation or catalysis, with a Zn/DMF system and subsequent treatment with allylic bromide afforded allylic sulfides in good to excellent yields.