2-d-1-(E)-丙烯基环丁烷向4-d-3-甲基环己烯的热异构化反应。

Thermal isomerizations of 2-d-1-(E)-propenylcyclobutanes to 4-d-3-methylcyclohexenes.

作者信息

Baldwin John E, Fedé Jean-Marie

机构信息

Department of Chemistry, Syracuse University, Syracuse, New York 13244, USA.

出版信息

J Am Chem Soc. 2006 May 3;128(17):5608-9. doi: 10.1021/ja0586586.

DOI:10.1021/ja0586586

Abstract

Racemic trans-2-d-1-(E)-propenylcyclobutane at 276 degrees C in the gas phase fragments to give ethylenes and pentadienes, equilibrates with its cis isomer, and rearranges to mixtures of 4-d- and 6-d-3-methylcyclohexenes through [1,3] carbon shifts. The time-dependent distributions of deuterium-labeled isomers of propenylcyclobutanes and 3-methylcyclohexenes reveal a significant secondary deuterium kinetic isotope effect favoring C1-C4 over C1-C2 bond breaking (kH/kD = 1.16 +/- 0.02) and a 72:28 preference for structural isomerizations giving (si + ar) rather than (sr + ai) products through conformationally flexible short-lived diradical intermediates.

摘要

外消旋反式-2-d-1-(E)-丙烯基环丁烷在276℃的气相中发生碎片化反应，生成乙烯和戊二烯，与顺式异构体达到平衡，并通过[1,3]碳迁移重排为4-d-和6-d-3-甲基环己烯的混合物。丙烯基环丁烷和3-甲基环己烯的氘标记异构体随时间变化的分布显示出显著的二级氘动力学同位素效应，有利于C1-C4键而非C1-C2键的断裂（kH/kD = 1.16 ± 0.02），并且通过构象灵活的短寿命双自由基中间体进行结构异构化时，生成(si + ar)产物而非(sr + ai)产物的比例为72:28。

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