A new access to substituted tetraethyl N-Boc 2-aminoethylidene-1,1-bisphosphonates and phosphonyl-substituted aza-Morita–Baylis–Hillman-type adducts

A general one-pot synthesis of substituted 2-aminoethylidene-1,1-bisphosphonates has been developed. The protocol involves base-induced addition of sodium tetraethyl methylenebisphosphonate to N-Boc imines generated in situ from N-Boc-α-amidoalkyl-p-tolylsulfones by the action of sodium hydride. The direct and efficient conversion of the title compounds into aza-Morita–Baylis–Hillman-type adducts has been also elaborated.