Sigmatropic isomerizations in azaallyl systems: XXI. Alkanimidoylphosphonates and their prototropic and phosphorotropic isomers

Abstract

Synthetic procedures for alkanimidoylphosphoryl derivatives with α-hydrogen atoms in the N-alkyl radical are developed. Data on the effect of substituents at the carbon and phosphorus atoms on the facility of prototropic transitions in the C=N-C triad are summarized. The most facile proton transfer occurs in the N-benzyl derivatives, and the prototropic isomer is the more stable, the stronger the electron-acceptor power of the substituent at the sp3-carbon atom of the azaallyl triad. The proton transfer in N-(α-phenethyl)-trifluoroacetimidoylphosphonates proceeds selectively, which allows preparation of enantiomerically enriched derivatives of α-aminotrifluoroethylphosphonic acid. A specific effect of substituents at the phosphorus atom on the prototropism attendant on phosphorylation of imidoyl chlorides is demonstrated.