ISSN:
0899-0042
Keywords:
conformational effect
;
intramolecular
;
allylic
;
stereogenic
;
steric
;
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
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.
Additional Material:
3 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/chir.530070208
