Thermal Reactions of <i>anti</i>- and <i>syn</i>-Dispiro[5.0.5.2]tetradeca-1,8-dienes: Stereomutation and Fragmentation to 3-Methylenecyclohexenes. Entropy-Dictated Product Ratios from Diradical Intermediates?
作者:W. von E. Doering、Juris L. Ekmanis、Kevin D. Belfield、F.-G. Klärner、Bernd Krawczyk
DOI:10.1021/ja004128s
日期:2001.6.1
independently from apposite, cis,trans geometric isomerizations can be successfully transferred to another system, in this paper, cyclobutanes. The first member of the series, 3-methylenecyclohexene (1), is photodimerized to anti- and syn-dispiro[5.0.5.2]tetradeca-1,8-dienes (anti-2 and syn-2), which undergo stereomutation (stereochemical interconversion) and cycloreversion (fragmentation) to 1 when heated
已经研究了一系列被具有增加自由基稳定能力的多烯取代的 1,2- 环丁烷,以测试独立于适当、顺式、反式几何异构化而获得的稳定能可以成功转移到另一个系统的命题,在本文中,环丁烷. 该系列的第一个成员 3-亚甲基环己烯 (1) 被光二聚化为反和顺-二螺[5.0.5.2]十四-1,8-二烯(反-2和syn-2),经过立体突变(立体化学当在 72.1-118.2 摄氏度范围内加热时,相互转化)和环转化(断裂)为 1:anti-2 --> syn-2,DeltaH() = 30.3 kcal mol(-)(1),DeltaS() = 0.2 cal mol(-)(1) K(-)(1); anti-2 --> 1, DeltaH() = 32.8 kcal mol(-)(1), DeltaS() = +8.0 cal mol(-)(1) K(-)(1)。通过假设在假设的双自由基中间体中完全烯丙基稳定来预