ZnCr 2 O 7 ·3H 2 O is a readily available and efficient reagent for the one-pot synthesis of a variety of thiosulfonates by chemoselective oxidation of thiols.Thiosulfonates have properties that make them attractive in biology, 1 industry, 2 and organic chemistry. 3 They show antimicrobial and fungicidal activities by blocking the normal metabolism of the microorganism via sulfonation of the enzyme's thiol groups. 1c Thiosulfonates have a wide industrial application both in polymer production and in photographic processes. 2 They have also been extensively utilized in organic synthesis due to their stronger sulfenylating power than disulfides and greater stability and easier handling than sulfinyl chlorides. 3There are several multistep approaches for the synthesis of thiosulfonates including selective reduction of sulfonyl chlorides, 4 reaction of thiosulfonates with diaryliodonium salts, 5 reaction of thiols with sulfonic acid using cyanuric chloride, 6 iodine/bromine oxidative sulfenylation of sulfinates with disulfides, 7 and oxidation of disulfides or thiosulfinates. 8 Thiosulfonates can also be prepared by onepot oxidation of thiols. A literature survey indicates that, in contrast to the numerous methods for the oxidation of thiols to disulfides, few methods are known for the direct synthesis of thiosulfonates from thiols by oxidation. 5,8a-c,9 Moreover, the existing methods suffer from limitations such as the need for special treatment for the activation of the reagent, difficult preparation or unavailability of the reagents, and lack of general applicability to thiol substrates bearing alkyl, aryl, cyclic, and heteroaromatic moieties. Hence, there remains the need for development of new protocols for the synthesis of these important scaffolds.Zinc dichromate trihydrate (ZnCr 2 O 7 ·3H 2 O) which is easily prepared by the reaction of ZnCO 3 with CrO 3 in acidic solution is a stable, cheap, and easy-to-handle compound. 10 It has been used as an efficient reagent for the oxidation of alcohols, sulfides, ethers, acetals, dithioacetals, oximes, silyl and pyranyl ethers. 11 We have recently reported oxidative deamination of amines and a-aminophosphonates, oxidation of a-hydroxyphosphonates, and oxidative deprotection of dithioacetals by ZnCr 2 O 7 ·3H 2 O. 12 To the best of our knowledge, there is no report on the oxidation of thiols by this reagent.In this paper, we wish to report a facile synthesis of thiosulfonates by a one-pot oxidation of thiols in the presence of ZnCr 2 O 7 ·3H 2 O at room temperature.
