Stereoselective Synthesis of Alkylphosphonates: A Facile Rearrangement of Cyanoethyl-Protected Nucleoside Phosphoramidites

Cyanoethyl-protected nucleoside phosphoramidites undergo a facile Michaelis−Arbuzov reaction upon addition of acrylonitrile to afford cyanoethyl phosphonates. This rearrangement is stereoselective at room temperature, but racemization is observed at high temperatures, indicating two different pathways. A plausible mechanism is proposed for this reaction.