Structure of 3-hydroxy-3-phenyl-pyrido[2,1-c][1,4]dihydrooxazinium bromide studied by X-ray, FTIR, 1H, 13C and 15N NMR, and DFT methods

2-Hydroxymethyl-pyridine with phenacyl bromide gives 3-hydroxy-3-phenyl-pyrido[2,1-c][1,4]dihydrooxazinium bromide (1). Its structure in crystal was determined by X-ray diffraction and confirmed by FTIR spectra and B3LYP calculations. In DMSO and D2O solutions, this compound exists in equilibrium mixtures with N-phenacyl-2-hydroxymethyl-pyridinium bromide (2). The equilibrium mixture was proved by FTIR, 1H, 13C and 15N NMR spectra. Correlations between the experimental 1H and 13C NMR chemical shifts for 1 and 2 and GIAO/B3LYP/6-31G(d,p) calculated magnetic isotropic shielding tensors (σ), δexp=a+bσcal, are reported. A good linear relationship between the experimental and calculated data was obtained only for carbons.