Synthesis of Thioglycosides by Tetrathiomolybdate-Mediated Michael Additions of Masked Thiolates

An efficient one-pot methodology for the synthesis of thioglycosides in excellent yields under neutral conditions through the use of benzyltriethylammonium tetrathiomolybdate $[{(BnNEt_3)}_2MoS_4; 1]$ as a sulfur-transfer reagent has been developed. The reagent 1 reacts with sugar halides to give sugar disulfides, which then undergo reductive cleavage in situ to provide the corresponding thiolates, followed by Michael addition to give the corresponding thioglycosides. Further, the utility of this one-pot reaction in aqueous medium has been exemplified through the use of ammonium tetrathiomolybdate $[{(NH_4)}_2 MoS_4; 2]$. The application of this methodology has been extended to the synthesis of a variety of thiosugar analogues with excellent diastereoselectivity through inter and intramolecular reactions