Recent Cyclization Reactions of 1-Alkynylphosphonates

This article describes the cyclization reactions of 1-alkynylphosphonates with an emphasis on the recent development in this field. Cyclopropyl-, cyclobutenyl-, cyclopentenyl-, cyclohexenyl-, and cycloheptenyl phosphonates were obtained either by amination of -chloroalkynylphosphonates or by addition of Lewis acid and copper chloride to zirconacyclopentenylphosphonate. On the other hand, cycloaddition of nitrile oxides or ethyl diazoacetate with perfluoroalkynylphosphonates produced heterocyclic phosphonates. In addition, 2-ethoxy-3-methylidene-1,2-hoxaphospholan-2-one rings were constructed by cyclization of 4-chlorobut-2-enyl ethyl alkynylphosphonate catalyzed by Pd(OAc),-LiC1.