STEREOCHEMISTRY OF THE THERMAL ISOMERIZATIONS OF (1R,2R)-1-((E)-STYRYL)-2-METHYLCYCLOPROPANE TO 3-PHENYL-4-METHYLCYCLOPENTENES
STEREOCHEMISTRY OF THE THERMAL ISOMERIZATIONS OF (1R,2R)-1-((E)-STYRYL)-2-METHYLCYCLOPROPANE TO 3-PHENYL-4-METHYLCYCLOPENTENES
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DOI：
10.1021/ja00076a021
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发表时间：
1993-11-17
影响因子：
15
通讯作者：
BONACORSI, S
中科院分区：
文献类型：
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作者：
BALDWIN, JE;BONACORSI, S
（1R，2R）-1 -（（E）-苯乙烯基）-2 -甲基环丙烷在250℃下发生外消旋化和异构化，生成6 -苯基-1,4 -（Z）-己二烯以及3 -苯基-4 -甲基环戊烯的四种异构体。从测得的外消旋化和结构异构化的速率常数，以及四种3 -苯基-4 -甲基环戊烯的相对含量随时间变化的信息可知，这种乙烯基环丙烷重排的四种立体化学上不同途径的相对贡献分别为60% si、10% ar、19% sr和11% ai。这四条动力学上相互竞争的途径的显著贡献，其参与的相对程度与反式-1 -（2 -氘乙烯基）-和反式-1 -（（E）-丙烯基）-2 -甲基环丙烷实验测定的结果相似，这意味着该重排既不受轨道对称性限制的支配，也不受依赖于转动惯量的旋转倾向的主导。
(1R,2R)-1-((E)-Styryl)-2-methylcyclopropane at 250-degrees-C racemizes and isomerizes to 6-phenylhexa-1,4-(Z)-diene and to the four isomers of 3-phenyl-4-methylcyclopentene. From the measured rate constants for racemization and for structural isomerizations, and from information on the relative amounts of the four 3-phenyl-4-methylcyclopentenes as a function of time, the relative contributions of the four stereochemically distinct paths for this vinylcyclopropane rearrangement have been found to be 60% si, 10% ar, 19% sr, and 11% ai. The substantial contributions from these four kinetically competitive paths, participating to relative extents similar to those experimentally determined for trans-1-(2-deuterioethenyl)- and trans-1-((E)-propenyl)-2-methylcyclopropanes, imply that the rearrangement is neither governed by orbital symmetry constraints nor dominated by moment-of-inertia-dependent rotational propensities.