Lewis base activation of Lewis acids. Addition of silyl ketene acetals to aldehydes

Scott E Denmark, Thomas Wynn, Gregory L. Beutner

Research output: Contribution to journalArticle

Abstract

The weak Lewis acid silicon tetrachloride can be activated by catalytic amounts of the chiral bisphosphoramide (R,R)-3 to form a highly reactive, chiral trichlorosilyl cation which is an extremely effective promoter of aldol addition reactions between aldehydes and silyl ketene acetals. The tert-butyldimethylsilyl ketene acetal of methyl acetate adds nearly instantaneously to aromatic and olefinic aldehydes as well as aliphatic aldehydes (albeit more slowly) with excellent enantioselectivity. The homologous tert-butyldimethylsilyl ketene acetal of tert-butyl propanoate adds with nearly exclusive anti diastereoselectivity to a similar range of aldehydes also with excellent enantioselectivity. The origin of the slower reaction rate with aliphatic aldehydes is revealed to be the formation of chlorosilyl ether adducts.

Original languageEnglish (US)
Pages (from-to)13405-13407
Number of pages3
JournalJournal of the American Chemical Society
Volume124
Issue number45
DOIs
StatePublished - Nov 13 2002

ASJC Scopus subject areas

  • Chemistry(all)

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