Article ID Journal Published Year Pages File Type
1314909 Journal of Fluorine Chemistry 2012 18 Pages PDF
Abstract

The TiCl4-mediated [3+3] cyclocondensation of 1,3-bis(silyloxy)-1,3-butadienes with 1-chloro-1,1-difluoro-4,4-dimethoxybut-3-en-2-one or 1,1-difluoro-4,4-dimethoxybut-3-en-2-one afforded CF2Cl- and CF2H-substituted salicylates, respectively. The Me3SiOTf-mediated [3+3] cyclocondensation of the same building blocks provided CF2Cl- and CF2H-substituted pyran-4-ones and CF2Cl-substituted cyclohexenones. The formation of CF2H-substituted cyclohexenones was not observed. Besides the type of Lewis acid, the product distribution is also influenced by the substitution pattern of the 1,3-bis(silyloxy)-1,3-butadiene: The Me3SiOTf mediated cyclization of C4-unsubstituted dienes resulted in the formation of CF2Cl-substituted pyran-4-ones, while the cyclization of C4-substituted dienes afforded CF2Cl-substituted cyclohexenones. The TiCl4-mediated cyclization of C4-substituted dienes with 1,1-difluoro-4,4-dimethoxybut-3-en-2-one failed. Therefore, 3-substituted CF2H-salicylates were prepared by transformation of the respective CF2Cl-salicylates with tributyltin hydride.

Graphical abstract6-Chlorodifluoromethylsalicylates and -pyran-4-ones are prepared by regioselective [3+3] cyclizations of 1,3-bis(silyloxy)-1,3-butadienes with CF2Cl-substituted 3-alkyloxy-2-en-1-ones. The regioselectivity is controlled by the choice of Lewis acid employed.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► The first formal [3+3] cyclizations of 1,3-bis(silyloxy)-1,3-butadienes with CF2Cl-substituted enones are reported. ► The first 6-chlorodifluoromethylsalicylates and pyranones are prepared. ► The reactions proceed with excellent regioselectivity. ► The regioselectivity can be controlled by the choice of Lewis acid.

Related Topics
Physical Sciences and Engineering Chemistry Inorganic Chemistry
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