Direct one-step synthesis of azaheterocyclic phosphonates from diethyl ω-chloro-1-alkynylphosphonates and hydrazines

Hydrazines react with 4-, 5- and 6-chloro-1-alkynylphosphonates to provide the corresponding azaheterocyclic phosphonates in good yields and purity. The suggested mechanism consists of initial addition to the carbon–carbon triple bond to generate a zwitterionic species in which the amine is situated trans to the lone pair of the anion.