The conformational energies of 2-methyl- and 4-methyl-1,3-dithiane. The breakdown of 1,3-syn diaxial repulsion hypothesis
作者:Douglas S Ribeiro、Roberto Rittner
DOI:10.1016/s0022-2860(03)00357-0
日期:2003.9
conformational energies of the methyl group at the 2 and 4 positions of the dithiane ring and that of methylcyclohexane, despite the larger distances between ring 1,3- syn - axial hydrogens and the closest methyl axial hydrogen in the dithiane ring. The possibility of a buttressing effect on the 2,4-dialkyl-1,3-dithianes previously studied and the rationale of 1,3- syn-axial steric interaction are discussed.
摘要 2-甲基- (-1.76 kcal mol -1 ) 和 4-甲基-1,3-二噻烷 (-1.75 kcal mol -1 ) 的构象焓 (Δ H ) 由 13 C 化学位移分析得到:温度的函数。这些能量与计算值 (B3LYP/6-31G(d,p)) 和基于 2,4-二烷基-1,3-二噻烷的文献值都非常吻合。结果证实了二噻烷环 2 和 4 位甲基的构象能与甲基环己烷的构象能相似,尽管环 1,3-顺轴氢和最接近的甲基轴向氢之间的距离更大。二噻烷环。讨论了对先前研究的 2,4-二烷基-1,3-二噻烷产生支撑作用的可能性以及 1,3- 同轴空间相互作用的基本原理。