Abstract The steric and electronic effects of acyl substituents COR (R = Me, i-Pr, Ph and t-Bu) upon conformational and keto—enol equilibria in 3-acyl-3,4-dihydrocoumarins have been studied by 1 H and 13 C NMR spectroscopy. With the increase of the effective size of R, preference for the equatorial position and the keto-form population increases considerably. The 13 C substituent-induced chemical shifts
摘要 1 H 和 13 研究了酰基取代基 COR(R = Me、i-Pr、Ph 和 t-Bu)对 3-酰基-3,4-二氢
香豆素的构象和酮-烯醇平衡的空间和电子效应。 C 核磁共振光谱。随着 R 的有效大小的增加,对赤道位置和酮型人口的偏好显着增加。还讨论了 13 C 取代基引起的
化学位移。