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The influence of protective groups on diastereofacial selectivity of Diels‐Alder cycloaddition reactions
Author(s) -
Gung Benjamin W.,
Mareska David A.,
Karipidis Anastas,
Henry Thomas
Publication year - 1995
Publication title -
chirality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.43
H-Index - 77
eISSN - 1520-636X
pISSN - 0899-0042
DOI - 10.1002/chir.530070208
Subject(s) - chemistry , allylic rearrangement , stereocenter , selectivity , intramolecular force , steric effects , ether , cycloaddition , stereochemistry , medicinal chemistry , intermolecular force , organic chemistry , molecule , catalysis , enantioselective synthesis
The diastereofacial selectivity of both inter‐ and intramolecular Diels‐Alder reactions with dienes having an allylic stereogenic center has been studied by varying the allylic oxygen protective group. Four different hydroxy protective groups were investigated including benzyl, t ‐butyldiphenylsilyl, triethylsilyl, and t ‐butyldimethylsilyl ethers. For intermolecular reactions, the benzyl ether derivative gave the highest sπ‐facial selectivity through a transition state in which the allylic stereocenter favors the CH eclipsed conformation. For intramolecular cycloadditions, the t ‐butyldimethylsilyl group gave a slightly higher selectivity than the benzyl ether derivative through a transition state in which the allylic stereocenter favors the CO eclipsed conformation. The opposite diastereofacial selectivity observed for inter‐ and intramolecular reactions is explained by considering both steric and electronic effects. © 1995 Wiley‐Liss, Inc.