Lewis acid catalysts Me3SiCl

The addition of substituted allylsilanes (68) to alkynes (66) in the presence of HfCl4 or EtAlCl2-Me3SiCl as Lewis acid catalysts produced the silylated 1,4-dienes (69) regio- and stereo-selectively in high yields in an exclusive trans-fashion (Scheme 16). The relative reactivities within the series are consistent with the involvement of cationic species (67) as intermediates.64... 

Carbon nucleophiles enols and enolates The direct Michael addition of enol acetates R CH=C(OAc)R to enones R CH=C(R )COR" has been attained using a combination of the Lewis acidic catalysts InCl3 and Me3SiCl, which generate stable enol-form intermedites4 ... 

Me3Si)2NH, Me3SiCl, Pyr, 20°, 5 min, 100% yield. ROH is a carbohydrate. Hexamethyldisilazane (HMDS) is one of the most common silylat-ing agents and readily silylates alcohols, acids, amines, thiols, phenols, hydroxamic acids, amides, thioamides, sulfonamides, phosphoric amides, phosphites, hydrazines, and enolizable ketones. It works best in the presence of a catalyst such as X-NH-Y, where at least one of the groups X or Y is electron withdrawing." Yttrium-based Lewis acids also serve as catalysts. ... 

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