A highly stereoselective TMSOTf-mediated catalytic carbocupration of alkynoates

The TMSOTf-mediated catalytic carbocupration of ynoates has been investigated. It has been shown that catalyst loadings as low as 5 mol % readily allow for high yields and diastereoselectivities for a series of aromatic Grignard reagents. In addition, we have been successful in vicinally functionalizing 1a via initial TMSOTf-mediated catalytic carbocupration followed by a secondary electrophilic capture of the TMS allenoate intermediate.