while the trans isomers show a high selectivity for 2:6 addition, which is explained by steric interactions. Introduction of a third substituent, OH or OCH3, on the alkenyl substituted carbon of the cyclohexane ring gives almost exclusively 1:3 addition. This can mostly be explained in terms of more steric hindrance in the conformations leading to 2:6 addition.
1-烯丙基-2-苯基
环己烷和1-苄基-2-
乙烯基环己烷的顺式异构体主要产生1:3加成,而反式异构体显示出2:6加成的高选择性,这可以通过空间相互作用来解释。在
环己烷环的链烯基取代的碳上引入第三取代基OH或OCH 3几乎仅以1:3加成。可以用导致2:6加成的构象中更大的位阻来解释这一点。