Phosphoramidates: Synthesis, spectroscopy, and X-Ray crystallography

A series of novel phosphoramidates with a general formula P(O)X1X2X3, where X1 = X2 = X3 = 1H-1,2,4-triazol (1); X1 = X2 = X3 = N-phenylhydrazine (2); X1 = Br, X2 = X3 = N-phenylhydrazine (3), X1 = Br, X2 = X3 = dipropylamine (4), and X1 = X2 = X3 = 1,4-dioxa-8-azaspiro[4.5]decane (5) as well as [P(O)(NC4H8NH-CH3)+3.3Cl-] (6), were synthesized and characterized by 1H, 13C, 31P NMR, IR spectroscopy, and elemental analysis. It is interesting that the P atoms of compounds 3 and 4 are the most upfielded atoms (d(31P) = -23.00, -21.65 ppm) among molecules 16. This indicates that the Br atom acts as a strong electron donor to the P atom via a resonance interaction. The 1H and 13C NMR spectra of compound 5 reveal three separate sets of peaks for the aliphatic CH2 protons of three four-membered rings. This can be explained by different spatial orientations (conformations) of the aliphatic rings. The crystal structure of compound 6 was also determined by X-ray crystallography. There are intermolecular N?H center dot center dot center dot Cl hydrogen bonds in this structure. (C) 2012 Wiley Periodicals, Inc. Heteroatom Chem 23:478485, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/hc.21040