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Stereoselective Disposition of the Geminal Dimethyl Group in the Cyclization of Geranyl Acetate under Zeolite Confinement Conditions
Author(s) -
Tsangarakis Constantinos,
Stratakis Manolis
Publication year - 2006
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.200600367
Subject(s) - chemistry , stereoselectivity , geminal , allylic rearrangement , carbocation , zeolite , double bond , medicinal chemistry , organic chemistry , nucleophile , solvolysis , stereochemistry , catalysis , hydrolysis
The stereochemistry in the acid‐catalysed biomimetic cyclization of [8,8,8‐D 3 ]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 (ClSO 3 H/2‐nitropropane) proceeds with negligible diastereoselectivity ( dr < 5 %). The enhanced diastereoselection within the zeolite is attributed to the proximity of the nucleophilic double bond to the intermediate carbocation, as a result of confinement (entropy effect). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)