A rapid injection NMR study of the chelation controlled Mukaiyama aldol addition: TiCl4 versus LiClO4 as the Lewis acid

Manfred T. Reetz, Burkhard Raguse, Charles F. Marth, Helmut M. Hügel, Thorsten Bach, David N.A. Fox

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78 Scopus citations

Abstract

The concept of chelation controlled addition to chiral alkoxy aldehydes using Lewis acids and mild C-nucleophiles has been extended to include cyclopropylation. The mechanism of the TiCl4-mediated chelation controlled addition of enolsilanes and allylsilanes to chiral α-alkoxy aldehydes has been studied by rapid injection NMR techniques. Accordingly, an acyclic transition state is involved in which the silyl group does not migrate to the carbonyl oxygen atom. In contrast, LiClO4 is an effective Lewis acid (excess or catalytic amounts) which induces chelation controlled group transfer type of aldol additions.

Original languageEnglish
Pages (from-to)5731-5742
Number of pages12
JournalTetrahedron
Volume48
Issue number27
DOIs
StatePublished - 3 Jul 1992
Externally publishedYes

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