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

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 α-haloketones and α-diazomethylphosphonates was developed. Pharmaceutically interesting chiral pyridazine-4­(1H)-ones were obtained in up to 98% yields with excellent stereoselectivities (up to 99% ee, > 99:1 dr).