Asymmetric Synthesis of Oxa‐Bridged Oxazocines through a Catalytic Rh^II/Zn^II Relay [4+3] Cycloaddition Reaction

Abstract

Oxa-bridged oxazocines bearing three chiral carbon centers were synthesized efficiently through ab imetallic catalytic asymmetric tandem reaction of b,g-unsaturated a-ketoesters with diazoimides.T he process contained ar hodiumpromoted in situ generation of isomünchnone from diazoimide decomposition, and a[ 4 + +3]-cycloaddition of b,g-unsaturated a-ketoester catalyzedb yachiral N,N'-dioxide-Zn II complex. Ligand-accelerated catalysis was found, and ap ossible transition-state model was proposed to explain the origin of stereoselectivity. Scheme 1. Cycloadditions involving isomünchnones.