Intramolecular hydrogen bonds in 1,4-dihydropyridine derivatives

1,4- dihydropyridine (1,4-DHP) derivatives have been synthesized and characterized by 1H, 13C, 15N NMR spectroscopy, secondary H/D 13C isotope shifts, variable temperature 1H NMR experiments and quantum-chemical calculation. The intramolecular hydrogen-bonds NH•••O=C and CH•••O=C in these compounds were established by NMR and quantum-chemical studies. The downfield shift of the NH proton, accompanied by the upfield shift of the 15N NMR signals, the shift to the higher wave numbers of the NH stretching vibration in the IR spectra and the increase of the 1J(15N,1H) values may indicate the shortening of the N-H bond length upon intramolecular NH•••O=C hydrogen bond formation.

1,4-二氢吡啶（1,4-DHP）衍生物已被合成，并通过1H、13C、15N核磁共振（Nuclear Magnetic Resonance，NMR）光谱、二级H/D 13C同位素位移、变温1H NMR实验以及量子化学计算完成表征。该类化合物中的分子内氢键NH•••O=C与CH•••O=C，已通过核磁共振与量子化学研究得以确证。NH质子的低场位移、伴随的15N NMR信号高场位移、红外光谱中NH伸缩振动波数向高波数偏移，以及1J(15N,1H)耦合常数的增大，均表明在形成分子内NH•••O=C氢键时，N-H键的键长发生了缩短。