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

Arunkumar Natarajan, Abraham Joy, Lakshmi S. Kaanumalle, John R. Scheffer, V. Ramamurthy

Research output: Contribution to journalArticle

24 Scopus citations

Abstract

Irradiation of 2-benzoyladamantane derivatives in zeolites yields the endo-cyclobutanols as the only photoproduct via a γ-hydrogen abstraction process. The cyclobutanols readily undergo retroaldol reaction to give δ-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 δ-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.

Original languageEnglish (US)
Pages (from-to)8339-8350
Number of pages12
JournalJournal of Organic Chemistry
Volume67
Issue number24
DOIs
StatePublished - Nov 29 2002
Externally publishedYes

ASJC Scopus subject areas

  • Organic Chemistry

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