Organocatalytic asymmetric synthesis of α-amino esters from sulfoxonium ylides

Described here is the first organocatalytic asymmetric N-H insertion reaction of alpha-carbonyl sulfoxonium ylides. Without a metal catalyst, this reaction represents an attractive complement to the well-established carbene insertion reactions. As a stable surrogate of diazocarbonyl compounds, sulfoxonium ylides reacted with a range of aryl amines to provide efficient access to alpha-aryl glycines with excellent enantiocontrol in the presence of a suitable chiral phosphoric acid catalyst. The high stability and weak basicity of sulfoxonium ylides not only enable this protocol to be user-friendly and practically useful, but also preclude catalyst decomposition, which is crucial to the excellent amenability to electron-poor amine nucleophiles. Detailed mechanistic studies indicated that the initial protonation is reversible and the C-N bond formation is rate-determining.

Automated summary

The research describes the first organocatalytic asymmetric N-H insertion reaction using alpha-carbonyl sulfoxonium ylides, providing efficient access to alpha-aryl glycines with excellent enantiocontrol. The high stability and weak basicity of sulfoxonium ylides make this protocol user-friendly and practically useful, with detailed mechanistic studies revealing reversible protonation and rate-determining C-N bond formation.