文章基本信息

标题：Stereochemical consequences of dynamic gearing in substituted bis(9-triptycyl) methanes and related molecules
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作者：W. Douglas Hounshell ; Constance A. Johnson ; Alberto Guenzi 等
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1980
卷号：77
期号：12
页码：6961-6964
DOI：10.1073/pnas.77.12.6961
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Empirical force-field calculations show that bis(9-triptycyl)methane has a Cs ground state and that the securely meshed triptycyl groups undergo nearly unhindered cogwheel rotation through a C2 transition state, with an activation energy of {approx}1.0 kcal mol-1. These features lead to note-worthy stereochemical attributes in appropriately substituted derivatives and analogs. Bis(9-triptycyl)carbinol has been prepared as an example of a compound that is chemically achiral, even though all conformations are chiral under the constraint of gear meshing. It is shown that, under the same constraint, ring substitution of either compound (or analogous systems) may lead to residual stereoisomerism. A permutational analysis of chemical isomers and isomerizations for every possible type of substitution pattern gives an enumeration of residual stereoisomers under the operation of various gearing and nongearing modes and provides information essential for a choice among mechanistic alternatives for a given isomer count.
关键词：cogwheel effects ; enantiomerization mechanisms ; residual stereoisomerism