Spectroscopic and DFT study of 3-quinolyl-α-aminophosphonates

Spectroscopic and DFT study of two types of 3-quinolyl-α-aminophosphonate derivatives obtained by one-pot microwave-assisted synthesis of quinoline-3-carboxaldehyde and aniline as well as 3-aminoquinoline and benzaldehyde, respectively, with diethyl phosphite, have been described. Besides the diethyl [α-anilino-N-(3-quinolylmethyl)]phosphonate (1) and diethyl [α-(3-quinolylamino)-N-benzyl]phosphonate (4) as the main reaction products, in both cases some unexpected monoester phosphonate derivatives were obtained as the by-products. In the first case along with diester 1, its corresponding monoethyl ester (2) and one monoethyl dihydrophosphonate-phosphate derivative (3) were formed, while in the second case diester 4 and a hydrogen phosphonamidate (5) were isolated. All quinoline-based α-aminophosphonates (1–5) have been characterized by IR spectroscopy, and the results obtained are compared and discussed with those obtained by the NMR studies. Combining experimental IR, 1H and 13C NMR spectra with DFT calculations, most intensive IR spectral bands of diesters 1 and 4, along with 1H and 13C NMR resonances of 1, 2 and 4 derivatives, were assigned.