S-Acylation of aliphatic and aromatic thiols with carboxylic acids and their esters over solid acid catalysts in the gas phase at temperatures above 200 °C

Authors:  Sayoko Nagashima, Hitomi Yamazaki, Kentaro Kudo, Satoshi Kamiguchi, Teiji Chihara

Abstract:
Benzenethiol is reacted with acetic acid in a hydrogen stream over [(Mo₆Cl₈)Cl₄(H₂O)₂]·6H₂O. Catalytic activity of the clusters appears above 200^◦C, yielding S-phenyl thioacetate. The selectivity is 98% at 300^◦C. Niobium, tantalum, and tungsten halide clusters with the same octahedral metal framework also catalyze the reaction. Benzoic acid and aliphatic carboxylic acids afford the corresponding S-phenyl carbothioates by reaction with benzenethiol. Aliphatic thiols are also S-acylated to yield the corresponding S-alkyl carbothioates. When carboxylic esters are applied to the reaction with benzenethiol over [(Nb₆Cl₁₂)Cl₂(H₂O)₄]·4H₂O at 450^◦C, the sterically unhindered moiety of the ester is incorporated into the products: S-phenyl thioacetate or methyl phenyl sulfide is obtained selectively. A Brønsted acid site developed on the cluster complex by thermal activation is the active site of the catalyst. Hence, solid acids such as silica–alumina, zeolites, and heteropoly acids that are stable above 200^◦C also catalyze these reactions.

Keywords:
S-Acylation
Thiol
Carboxylic acid
Carboxylic ester
Brønsted acid

Published in: Applied catalysis A: General  (Volumes 464–465, Pages 1-384, 15 August 2013)

Publisher: Elsevier  

ISSN Information: 0926-860X

S-Acylation of aliphatic and aromatic thiols with carboxylic acids and their esters over solid acid catalysts in the gas phase at temperatures above 200 °C

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