Structural Effects in NMR Spectroscopy of Vinylic Compound 1. Investigation of Intramolecular Specific Interactions C–H···N in Hetaryl Vinyl Ethers by 1H, 13C, 15N, and 17O NMR Spectroscopies and Quantum-Chemical Calculations

Abstract

Abstract The hydrogen bond-like intramolecular specific interactions between the α-hydrogen of the vinyl group and endo-cyclic nitrogen are discovered in the hetaryl vinyl ethers, having the vinyloxyl group neighboring to the endocyclic nitrogen by the 1H and 13C NMR data. It is confirmed by AM1 calculations. The intramolecular specific interaction results to the downfield shift of the α-proton signal by 1 ppm, α-carbon signal by 4—5 ppm, the increase of their one-bond coupling constant by 6—7 Hz, and upfield shift of nitrogen by 17—20 ppm, as it was shown by the regression and dispersion analysis of 1H, 13C, and 15N parameters of wide series of aryl and hetaryl vinyl ethers. The cluster analysis of the spectral data indicates the anomaly of common combination of vinyloxyl group parameters in ethers, possessing the intramolecular specific interaction in comparison with ethers which have no such interaction. The factor analysis of spectral parameters shows that influence of specific interaction on the α-proton and α-carbon chemical shifts as well as their one-bond coupling constant prevails over other structural and electronic effects. In accordance with the AM1 calculation, the hetaryl vinyl ethers possessing the intramolecular specific interaction are more planar that is confirmed by 13C and 17O NMR data.