One-Pot Synthesis of Glycosyl Chlorides from Thioglycosides Mediated by a Bromodiethylsulfonium Salt as a Mild Oxidant

Abstract

AbstractThe conventional synthesis of glycosyl chlorides from thioglycosides relies on sequential oxidation and chlorination. A one-pot synthesis of glycosyl chlorides is warranted as an alternative method. Here, we report a one-pot synthesis of glycosyl chlorides from thioglycoside precursors. The transformation was mediated at low temperatures by bromodiethylsulfonium bromopentachloroantimonate (BDSB) as a mild oxidant with Bu4NCl as an additive. Armed thioglycosides afforded the corresponding α-glycosyl chlorides in moderate to good yields under the optimized conditions. Low conversions and yields were obtained when the less-reactive disarmed thioglycosides were used. Unexpectedly, BDSB-mediated oxidation of thioglycosides without the addition of Bu4NCl also afforded the α-glycosyl chlorides in moderate yields. We suggest a mechanism involving the transfer of chloride ions from the nonnucleophilic bromopentachloroantimonate (SbCl5Br) anion to the oxocarbenium ion.