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Synthesis 2012(6): 857-861  
DOI: 10.1055/s-0031-1290157
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© Georg Thieme Verlag Stuttgart ˙ New York

Facile Synthesis of Substituted 1,1-Difluoroallenes via Carbonyl Difluorovinylidenation

Ken Oh, Kohei Fuchibe, Misaki Yokota, Junji Ichikawa*
Department of Chemistry, Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8571, Japan
Fax: 81(29)8534237; e-Mail: junji@chem.tsukuba.ac.jp;
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Publication History

Received 22 November 2011
Publication Date:
16 January 2012 (online)

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Abstract

Two methods for the difluorovinylidenation of carbonyl compounds have been developed to synthesize 1,1-difluoroallenes bearing various substituents. The reaction of 1-bromo-2,2-difluorovinyllithium, generated from 1,1-dibromo-2,2-difluoroethylene and n-butyllithium, with aldehydes or ketones, and subsequent acetylation, gives 2-bromo-3,3-difluoroallylic acetates. Elimination of these acetates with n-butyllithium affords 1,1-difluoroallenes in high yield. 3,3-Difluoro-2-iodoallylic acetates are similarly prepared from aldehydes or ketones on treatment with 2,2-difluoro-1-iodovinyllithium, generated from 1,1,1-trifluoro-2-iodoethane and lithium diisopropylamide, followed by acetylation. These acetates readily undergo elimination with zinc metal to afford 1,1-difluoroallenes in high yield.

Key words

carbonyl compounds - metalation - difluorovinylidenation - 1,1-difluoroallenes

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