pH-Dependence of the Aqueous Phase Room Temperature Brønsted Acid-Catalyzed Chemoselective Oxidation of Sulfides with H2O2

Abstract

A pH-dependence of the Brønsted acid-catalyzed oxidation of sulfides to the corresponding sulfoxides with H2O2 is reported for the first time based on our systematic investigation of the catalytic performance of a series of Brønsted acids. For all of the Brønsted acids investigated, the catalytic performances do not depend on the catalyst loading (mol ratio of Brønsted acid to substrate), but rather depend on the pH value of the aqueous reaction solution. All of them can give more than 98% conversion and selectivity in their aqueous solution at pH 1.30, no matter how much the catalyst loading is and what the Brønsted acid is. This pH-dependence principle is a very novel perspective to understand the Brønsted-acid catalysis system compared with our common understanding of the subject.

A Concise Review on Synthesis of Sulfoxides and Sulfones with Special Reference to Oxidation of Sulfides

“…He has concluded that, the performance of the catalyst in this oxidation does not depend upon the amount of the catalyst but it depends upon the pH of the reaction medium. With the choice of any Bronsted acid as catalyst at pH 1.30, more than 98 % conversion with high selectivity and excellent substrate tolerance has been reported (Scheme 15) [99].…”