作者:Harold Booth、Khedhair A. Khedhair、Hatif A.R.Y. Al-Shirayda
DOI:10.1016/s0040-4020(01)85926-3
日期:1988.1
The positions of conformational equilibria due to the double ring inversion in cis-decahydroquinazoline (7 ⇄ 8) and cis-decahydro-3-methylquinazoline (9 ⇄ 10) were determined by 13C n.m.r. spectroscopy in the range 215-225 K. In both cases there is a very strong preference (-ΔG7→8o 1.08 kcal mol-1; -ΔG9→10o 1.10 kcal mol-1) for the conformation which would allow the lone pairs on N(1) and N(3) to lie
通过13 C nmr光谱在215-225 K范围内测定了顺式十氢喹唑啉(778 )和顺式十氢-3-甲基喹唑啉(9910)中双环倒置引起的构象平衡位置。的情况下,构象有一个非常强烈的偏好(-ΔG7 →8 o 1.08 kcal mol -1;-ΔG9 →10 o 1.10 kcal mol -1),这将允许在N(1)和N(3 )躺在分子受阻的“内部”面上。但是,值3顺式十氢-3-甲基喹唑啉(10)和顺式(4aH,8aH)顺式(2H,8aH)-十氢-2,3-二甲基喹唑啉(14)的J(CHNH)耦合常数表明N在N(1)更喜欢N(1)-H位于“内侧”(轴向)且N(1)-孤对赤道的构象,因此证明了端基异构化作用胜过空间排斥的能力。