Phosphazene base, P2-tBu, efficiently catalyzed the telescopic three-component reaction of diethyl phosphite, cinnamonitrile derivatives, and N-Boc imines, providing β-aminophosphonates having a tetrasubstituted carbon in a highly diastereoselective manner. The reaction involves the little-known 1,1-difunctionalization of an electron-deficient alkene, offering a new format for the three-component reaction under Brønsted base catalysis.