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