Substoichiometric TiCl4-mediated vicinal difunctionalization of α,β-acetylenic ketones for the synthesis of β-halo Baylis-Hillman olefins

Han Xun Wei, Ju J. Gao, Guigen Li

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27 Scopus citations

Abstract

A substoichiometric amount of titanium tetrachloride was found to be effective to promote and participate in the tandem α-hydroxyalkylation/β-chlorination of α,β-acetylenic ketones in the presence of (n-Bu)4NI. This method provides the concise synthesis of (E)-β-halo Baylis-Hillman adducts. No β-iodo products were detected when using this combination of halogen sources. The reaction process involves 1,4-addition of chloro anion released from TiCl4 onto α,β-acetylenic ketones to give TiCl3-allenolate intermediates followed by the titanium Lewis acid-promoted carbonyl addition. Modest to good yields (53-77%) and excellent E/Z stereoselectivity (>95%) have been obtained for 10 examples.

Original languageEnglish
Pages (from-to)9119-9122
Number of pages4
JournalTetrahedron Letters
Volume42
Issue number52
DOIs
StatePublished - Dec 24 2001

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