Abstract
A simple, efficient, and selective oxidation under flow conditions of sulfides into their corresponding sulfoxides and sulfones is reported herein, using as a catalyst perselenic acid generated in situ by the oxidation of selenium (IV) oxide in a diluted aqueous solution of hydrogen peroxide as the final oxidant. The scope of the proposed methodology was investigated using aryl alkyl sulfides, aryl vinyl sulfides, and dialkyl sulfides as substrates, evidencing, in general, a good applicability. The scaled-up synthesis of (methylsulfonyl)benzene was also demonstrated, leading to its gram-scale preparation.
Highlights
Heteroatom oxidation, with particular emphasis on nitrogen and sulfur, is a process of great relevance in organic synthesis
We demonstrated that as the selenium atom of the glutathione peroxidase enzyme catalyzes the oxidation of two molecules of glutathione using peroxides as stoichiometric oxidants, small organoselenium molecules can be biomimetically used as catalysts in the hydrogen-peroxide-mediated oxidation of thiols [12]
Over the last ten we have studied the applicability of selenium derivatives as catalysts in and the beneficial effects on the reactivity and selectivity, as well as the reaction workup, product biomimetic oxidations, demonstrating that this approach presents a number of advantages in terms purification, and recovery of eco-sustainability
Summary
Heteroatom oxidation, with particular emphasis on nitrogen and sulfur, is a process of great relevance in organic synthesis. For the oxidation of sulfides into their corresponding sulfoxides and sulfones, a number of procedures have been described, including stoichiometric reactions, chemocatalytic reactions, and bio-catalytic reactions [1]. Arylsulfones and arylsulfoxides are useful synthetic intermediates and building blocks for the synthesis of a series of biologically active compounds [2,3]. A non-exhaustive panel of examples is presented in Figure 1: an arylsulfone moiety is present in drugs like Rofecoxib (I) [4], Laropiprant (II) [5], Dapson (III) [6], and Sulfamethoxazole (IV) [7], while examples of arylsulfoxides (even if less distributed due to their relative instability) can be found in Sulindac (V) a clinically used anti-inflammatory drug [8], in esomeprazole (VI), the S enantiomer of omeprazole [9], and in a recently reported compound (VII) with anti-HIV activity [10].
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