Stereoselective Disposition of the Geminal Dimethyl Group in the Cyclization of Geranyl Acetate under Zeolite Confinement Conditions
作者:Constantinos Tsangarakis、Manolis Stratakis
DOI:10.1002/ejoc.200600367
日期:2006.10
The stereochemistry in the acid-catalysed biomimetic cyclization of [8,8,8-D3]geranyl acetate was examined in solution and under conditions of zeolite Y confinement. In the intrazeolite reaction the gem-allylic methyl group adopts a diastereoselective disposition in the cyclization product (64 % dr). In contrast, the gem-dimethyl disposition in a homogeneous medium (ClSO3H/2-nitropropane) proceeds
[8,8,8-D3] 香叶基乙酸酯的酸催化仿生环化中的立体化学在溶液中和沸石 Y 限制条件下进行了检查。在沸石内反应中,偕烯丙基甲基在环化产物中采用非对映选择性配置 (64 % dr)。相比之下,在均质介质 (ClSO3H/2-硝基丙烷) 中的 gem-二甲基处置以可忽略不计的非对映选择性 (dr < 5%) 进行。作为限制(熵效应)的结果,沸石内增强的非对映选择归因于亲核双键与中间碳正离子的接近。(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)