Synthesis of novel α-aminophosphonates by methanesulfonic acid catalyzed Kabachnik–Fields reaction

A series of novel α-aminophosphonates of diethyl (2,4-difluorobenzylamino)methylphosphonate derivatives (4a–4g) have been synthesized by applying three-component Kabachnik–Fields reaction, using fluoro derivatives of aldehydes and substituted amines, diethyl phosphonate in the presence of a catalytic amount of methanesulfonic acid (MSA) in good yields with high enantioselectivities (up to 98% ee). The enantioselectivitiy of compounds (4a–4g) was confirmed by chiral HPLC. The direct Kabachnik–Fields reaction with high reactivity under mild reaction conditions and significantly used for synthesis of the α-aminophosphonate. The novel products were characterized by spectral and analytical data.