Free radical reaction of α-haloalkylphosphonates with alkenes and alkynes: A new approach to modified phosphonates

Article abstract of DOI:10.1055/s-1995-3914

A new approach to the synthesis of phosphonates 3 functionalized in the α- and γ-phosphonate positions by alkyl, ethoxy, butoxy, acetoxy, acetyl and cyanide groups and allylphosphonate 6 is described. It is based on the radical reaction of α-halosubstituted phosphonates 1 (X = Cl, Br, I) with the terminally unsubstituted alkenes 2 (1-heptene, ethoxyethene, butoxyethene, acetoxyethene, acrylonitrile, methyl vinyl ketone) and alkyne 5 (hept-1-yne). The reaction involving the tin hydride method (Bu₃SnH/AIBN) was more effective with alkenes than with alkynes (40-72% versus 20-30%). With electron-rich alkenes, chloro- and bromomethylphosphonates 1 (X = Cl, Br) gave higher yields than iodomethylphosphonate 1 (X = I). Diethyl methylphosphonate 4, as a reduction product of 1, accompanied 3 and 6 in the above reactions. The yield of 4 could be reduced by optimizing the reaction conditions.