Resolution of sterically overcrowded ethylenes; a remarkable correlation between bond lengths and racemization barriers.
作者:Ben L. Feringa、Wolter F. Jager、Ben de Lange
DOI:10.1016/s0040-4039(00)78887-3
日期:1992.5
The synthesis and resolution of 2-methyl-9H-thioxanthene-9-(9H-thioxanthen-9-ylidene) 1 and related structures 2-5, being the first examples of thermally stable optically active sterically overcrowded ethylenes, are reported. Substitution of the sulfur atom in the thioxanthene part of 1 with an X group (2, X = C(CH32; 3, NCH3 4, O) results in a change in racemization barrier (1, 27.4 kcal.mol−1; 3
据报道,作为热稳定的光学活性的空间上过度拥挤的乙烯的第一个实例,2-甲基-9H-噻吨蒽-9-(9H-噻吨酮-9-亚烷基)1和相关结构2-5的合成和拆分。1的噻吨并蒽部分中的硫原子被X基团取代(2,X = C(CH 3 2 ; 3,NCH 3 4,O)导致消旋化势垒的改变(1,27.4 kcal.mol -1; 3,21.3kcal.mol 1 4,<20 kcal.mol -1),这取决于芳基-X键的长度。