Catalytic Asymmetric (3 + 3) Cycloaddition of Oxyallyl Zwitterions with α-Diazomethylphosphonates

Abstract

The unique structure of oxyallyls represents a significant challenge for their catalytic asymmetric applications. Herein, an unprecedented chiral imidodiphosphoric acid-catalytic enantioselective (3 + 3) cycloaddition between oxyallyl zwitterions generated in situ from a-haloketones and alpha-diazomethylphosphonates was developed. Pharmaceutically interesting chiral pyridazine4(1H)-ones were obtained in up to 98% yields with excellent stereoselectivities (up to 99% ee, > 99:1 dr).