Research & Teaching Faculty

Default Header Image

Enhanced enantio- and diastereoselectivity via confinement and cation binding: Yang photocyclization of 2-benzoyladamantane derivatives within zeolites

TitleEnhanced enantio- and diastereoselectivity via confinement and cation binding: Yang photocyclization of 2-benzoyladamantane derivatives within zeolites
Publication TypeJournal Article
Year of Publication2002
AuthorsNatarajan, A, Joy, A, Kaanumalle, LS, Scheffer, JR, Ramamurthy, V
JournalJournal of Organic Chemistry
Volume67
Pagination8339-8350
Date PublishedNov
Type of ArticleArticle
ISBN Number0022-3263
KeywordsABSOLUTE ASYMMETRIC-SYNTHESIS, ACID-DERIVATIVES, CATALYSTS, COMPLEXES, EPOXIDATION, INDUCTION, PHOTOREACTIONS, SOLID-STATE, STATE ORGANIC-PHOTOCHEMISTRY, TROPOLONE ETHER
Abstract

Irradiation of 2-benzoyladamantane derivatives in zeolites yields the endo-cyclobutanols as the only photoproduct via a gamma-hydrogen abstraction process. The cyclobutanols readily undergo retro-aldol reaction to give delta-ketoesters. The enantiomeric excess (ee) in the endo-cyclobutanols is measured by monitoring the ee in the ketoesters. Whereas in solution the ee in the product ketoester is zero, within achiral NaY zeolite, in the presence of a chiral inductor such as pseudoephedrine, ee’s up to 28% have been obtained. The influence of zeolite on several chiral esters of 2-benzoyladamantane-2-carboxylic acids has also been examined. Whereas in solution the diastereomeric excess is <15%, in zeolite the delta-ketoesters are obtained in 79% de (best examples). Ab initio computations suggest that enhancement of chiral induction within zeolites is likely to be due to cation complexation with the reactant ketone. Alkali ion-organic interaction, a powerful tool, is waiting to be fully exploited in photochemical and thermal reactions. In this context zeolites could be a useful medium as one could view them as a reservoir of "naked" alkali ions that are only partially coordinated to the zeolite walls.

URL<Go to ISI>://000179509400006