Synthesis and spectroscopic study of a new diamidophosphoester, (4-CH3-C6H4O)((CH3)2CHNH)2P(O)

A new diamidophosphoester, (4-CH3-C6H4O)((CH3)2CHNH)2P(O), was synthesized from the reaction of freshly prepared (4-CH3-C6H4O)Cl2P(O) reagent and isopropylamine (1:4 mole ratio) in dry CH3CN. The prepared compound was characterized by IR, 1H-NMR, 13C{1H}-NMR and 31P{1H}-NMR spectroscopies. Two methyl groups of the NHCH(CH3)2 moiety are magnetically non-equivalent and are revealed in different chemical shifts in the 1H- and 13C-NMR spectra, but with equal hydrogen-hydrogen coupling constants in 1H-NMR (3J(H,H) = 6.4 Hz for both) and phosphorus-carbon coupling constants in 13C-NMR (3J(P,C) = 5.7 Hz for both). The NH protons reveal a triplet with apparent coupling constant of 10.1 Hz (due to geminal phosphorus-hydrogen and vicinal hydrogen-hydrogen couplings). The ipso and ortho carbon atoms of the 4-CH3-C6H4O moiety appear as doublets with 2J(P,C) = 6.5 Hz  3J(P,C) = 4.8 Hz. In the IR spectrum, the NH stretching vibrations appear at 3281 cm–1 and 3194 cm–1. The phosphorus chemical shift of the title compound was compared with some literature compounds to show the electronic and anisotropic effects of substituents attached to phosphorus.