Trimethyl Phosphite as a Trap for Alkoxy Radicals Formed from the Ring Opening of Oxiranylcarbinyl Radicals. Conversion to Alkenes. Mechanistic Applications to the Study of C−C versus C−O Ring Cleavage
作者:Bangwei Ding、Wesley G. Bentrude
DOI:10.1021/ja020761x
日期:2003.3.1
and C-C (k(2)) cleavages of intermediate oxiranylcarbinyl radical 2 and their reverse (k(-1), k(-2)). Diversion by (MeO)(3)P of allyloxy radicals (3) from haloepoxides 11 and 12 fulfills a prior prediction that under conditions closer to kinetic control, products of C-O scission, not just those of C-C scission, may result. Thus, for oxiranylcarbinyl radicals from haloepoxides 11, 12, and 13, C-O scission
亚磷酸三甲酯 (MeO)(3)P 作为有效和选择性陷阱引入环氧乙烷基自由基 (2) 系统中,该系统由卤代环氧化物 8-13 在约 80 摄氏度的热 AIBN/n-Bu(3)SnH 条件下形成最初,在不存在亚磷酸酯的情况下,8-13 向烯丙醇 7 和/或乙烯基醚 5 的转化被定量测量(表 1)。中间体环氧乙烷基 (2)、烯丙氧基 (3) 和乙烯基氧基羰基 (4) 自由基的结构变化涉及 CO (2 --> 3, k(1)) 和 CC (2 --> 4, k(2)) 自由基断裂过程,并且很容易解释形成的产物乙烯基醚 (5) 和烯丙醇 (7) 的量的变化。添加的 (MeO)(3)P 对乙烯基氧羰基自由基 4 呈惰性,并选择性地快速捕获烯丙氧基自由基 3,将其转移到磷酸三甲酯和烯丙基 6。烯丙基 (6) 二聚化或被 n-Bu(3)SnH 捕获以产生烯烃,由卤代环氧化物 8、9 和 13 形成,产率为