Unusual dephosphorylation of enamine phosphonate

Abstract

While attempting to synthesize the $\beta$-amino phosphonate from reduction of $\beta$-enamino phosphonate intermediate, it was found that selective dephosphorylation of $\beta$-enamino phosphonates occured by $LiAlH_4$ and the corresponding ketones were produced. Also it was proved that $\beta$-keto phosphonate, as an analog of $\beta$-enamino phosphonate, undergoes dephosphorylation under the same conditions. To gain insight about the mechanism of this reaction, several experiments were carried out as depicted and plausible mechanism was proposed. Several reductants were examined to find the optimun conditions, and $LiAlH_4$ gave the best result. In conclusion, dephosphorylation reaction of $\beta$-enamino phosphonate can be used as a good method to prepare ketones from aromatic nitriles.