The Utilization of Carbene Catalysis and Different Synthetic Strategies for Sydnone Construction

Abstract

Here, the synthesis of benzoin was conducted using carbene precatalyst bis(amino)cyclopropenylidene (BAC-H) with multiple different bases that are used in literature. It was determined that the combination of bases sodium hydride and KHMDS provided moderate yields of benzoin. Further optimization studies were then commenced to increase the yield followed by the investigation of the scope. Further, different catalytic strategies for the cyclization of sydnones were also investigated including the utilization of the Vilsmeier –Haak reagent and triphenylphosphine oxide to provide fast reactions and excellent yields. Both of these catalytic methods were optimized, and broad substrate scopes were demonstrated in high yields. These findings are supported by DFT studies and the calculations of the procedure’s green metrics.