Rh-Catalyzed three-component reaction for the diastereoselective synthesis of pyrazolone derivatives with contiguous quaternary stereocenters

A diastereoselective three-component reaction of diazo compound with alcohol and pyrazolinone ketimine by utilizing rhodium(II) catalysis via interception of transient oxonium ylides was reported. The reaction provides an efficient approach for the facile construction of polyfunctionalized pyrazolone derivatives bearing two contiguous quaternary stereocenters in good yields with high regioselectivities and excellent diastereoselectivities.