We describe the synthesis of new gem-difluoro-C-silylated aldols from acylsilanes and trifluoromethyltrimethylsilane via an aldol reaction. Their defluorosilylation gives aliphatic and alicyclic 2-fluoro-1,3-diketones. The overall reaction sequence can be considered as a new complementary method giving access to a wide variety of such fluorinated 1,3-diketones.
Abstract The optimization of the synthesis of 2,6-bis(trialkylsilyl)4H-thiopyranes and some aspects of the reactivity of the corresponding lithium salts with alkyl halides and benzaldehyde are presented.
Bis(acylsilanes) and Trifluoromethyltrimethylsilane: A Useful System for the Synthesis of Cyclic 2,2-Difluoro-3-trialkylsilyl-1,3-ketols and Cyclic 2-Fluoro-1,3-diketones<sup>1</sup>
silylketols 4. These compounds were submitted to a facile and effective defluorosilylation. The overall process constitutes a new synthesis of cyclic six- and seven-membered 2-fluoro-1,3-diketones 8, with regiospecific introduction of fluorine. The keto-enolequilibrium of cyclic 1,3-diketones and the mechanism of the defluorosilylation reaction were also studied.
The new 2,6-bis-trialkylsilyl-4H-pyranes were easily prepared from 1,5-bisdithianes via a two steps sequence of dethioketalization and cyclodehydration in the presence of a catalytic amount of p-toluenesulfonic acid. (C) 1999 Elsevier Science Ltd. All rights reserved.
Synthesis of new silylated sulfur-containing heterocycles through thionation of bis(acylsilanes)
The thionation of bis(acylsilanes) with spacers of variable size with hexamethyldisilathiane under cobalt(II) chloride or trimethylsilyl triflate catalysis affords 2,5-bis(trialkylsilyl)-thiophenes , 2,6-bis(trialkylsilyl)-4H-thiopyrans and 2,7-bis(trialkylsilyl)4,5-dihydrothiepine generally along with a minor amount of the corresponding oxo analogue. The synthesis of both symmetrical and unsymmetrical bis(trialkylsilyl) derivatives was achieved. (C) 2003 Elsevier Ltd. All rights reserved.