Modification of Face Selectivity by Inclusion in Cyclodextrins

Wen-Sheng Chung, Nicholas J. Turro, Jack Silver, William J. le Noble

Research output: Contribution to journalArticle

51 Scopus citations

Abstract

The photocycloadditions of 5-X-adamantan-2-ones (5-X-AD, where X = F, Cl, Br, OH, Ph, and t-Bu) with fumaronitrile have been studied in acetonitrile and in aqueous solutions. When X is Cl, Br, Ph, or t-Bu, irradiation of an aqueous solution containing β-cyclodextrin (β-CD) leads to a dramatic reversal in face selectivity compared to that found in acetonitrile and water; however, there is no significant change in product ratio compared to that found in aqueous solution in the presence of α- and γ-CD. The effect observed with β-CD is interpreted with the assumption that the carbonyl π face syn to the bulky 5-substituent is partially blocked by the torus of the host due to complexation of the AD and CD. 1H NMR and concentration dependence studies provide support for this interpretation. Similar reversals of face selectivity upon complexation with (β-CD are observed in the thermal reduction of these ketones by sodium borohydride. It is also noted that a much enhanced syn hydride delivery occurs in water as compared to organic solvents and that this enhancement vanishes upon cooling.

Original languageEnglish
Pages (from-to)1202-1205
Number of pages4
JournalJournal of the American Chemical Society
Volume112
Issue number3
DOIs
StatePublished - 1 Jan 1990

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