A Streamlined Regenerative Glycosylation Reaction: Direct, Acid‐Free Activation of Thioglycosides

<div class="line" id="line-13"> <br/></div><div class="line" id="line-24"> <span style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 14px;'> Direct conversion&nbsp;of thioglycosides via the regenerative approach that bypasses the intermediacy of glycosyl bromides and eliminates the need for heavy metal-based promoters is reported. The direct regenerative activation of thioglycosides is achieved under neutral reaction conditions using only 1&emsp14;equiv. NIS and catalytic 3,3-difluoroxindole (HOFox) without the acidic additives. </span></div><div class="line" id="line-32"> <span style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> Our group has previously reported that 3,3-difluoroxindole (HOFox) is able to mediate glycosylations via intermediacy of OFox imidates. Thioglycoside precursors were first converted into the corresponding glycosyl bromides that were then converted into the OFox imidates in the presence of Ag </span> <span style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 12px;'> 2 </span> <span style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> O followed by the activation with catalytic Lewis acid in a regenerative fashion. Reported herein is a direct conversion of thioglycosides via the regenerative approach that bypasses the intermediacy of bromides and eliminates the need for heavy-metal-based promoters. The direct regenerative activation of thioglycosides is achieved under neutral reaction conditions using only 1&emsp14;equiv. NIS and catalytic HOFox without the acidic additives. </span></div>