Photo-induced phosphorylation/cyclization of N -homoallyl and N -allyl aldehyde hydrazones to access phosphorylated tetrahydropyridazines and dihydropyrazoles.

A photocatalytic radical carbophosphorylation/cyclization of N -homoallyl aldehyde hydrazones with phosphine oxides was developed under metal-free conditions, achieving phosphorylated tetrahydropyridazines in yields up to 95%. Phosphorylated dihydropyrazoles were also constructed, by reacting N -allyl aldehyde hydrazones with phosphine oxides under the same conditions.