1-Phenyl-1,2-cyclohexadiene: Astoundingly High Enantioselectivities on Generation in a Doering-Moore-Skattebøl Reaction and Interception by Activated Olefins
作者:Manfred Christl、Hartmut Fischer、Mario Arnone、Bernd Engels
DOI:10.1002/chem.200900718
日期:2009.10.26
from (−)‐5 and was enantiospecifically intercepted to give the product. In the case of indene as trap for (M)‐7, the (−)‐ and the (+)‐enantiomer of the [2+2] cycloadduct were formed in the ratio of 95:5. Highly surprising, remarkable enantioselectivities were also observed, when (M)‐7 was trapped with styrene to furnish two diastereomeric [2+2] cycloadducts. Hence, the achiral conformation of the diradical
的(1α,5α,6α)分辨率-6-溴-6-氟-1-苯基二环[3.1.0]己烷(外消旋- 5)所提供的对映体纯的前体( - ) - 5和(+) - 5的1-苯基-1,2-环己二烯。在2,5-二甲基呋喃存在下用甲基锂处理(−)‐ 5时,将2,5‐二甲基呋喃的[4 + 2]环加合物的纯(−)‐对映异构体附着在1‐苯基‐1,2‐2‐仅获得环己二烯。从该结果可以得出结论,纯净的(M)-1-苯基-1,2-环己二烯((M)-7)从(−)- 5出来,被对映体截获,得到产物。如果使用茚作为(M)的阱-如图7所示,[2 + 2]环加合物的(-)-和(+)-对映异构体以95:5的比例形成。当(M)-7被苯乙烯捕获以提供两个非对映异构[2 + 2]环加合物时,也观察到了令人惊讶的惊人对映选择性。因此,可以想象为中间体的双自由基的非手性构型不能起决定性的作用。还测试了通过β消除途径生成的(M)‐和(P)‐7对映选择性。因此,在2