Allylsilanes with acyl halides

Similar conditions are used to effect reactions of allylsilanes with acyl halides, resulting in (3,y-unsaturated ketones.128... 

Titanium tetrachloride is a useful Lewis acid for the addition of other electrophiles to allylsilane these electrophiles include acid anhydrides (Eq. 85) [229], acyl halides (Eq. 86) [2,3,159,161,230], and SNl-active halides such as rert-alkyl halides (Eq. 87) [165] and a-halosulfides [2,3,159,161]. The allylation of the substrate shown in Eq. (88) was accompanied by stereoselective opening of the cyclobutane ring to give an open-chain triene with defined olefin geometry [231]. A benzylic selenonium... 

Although the direct generation of titanium enolates is typically the most useful method of generating titanium enolates for aldol reactions, other methods have been described. Grubbs and Stille reported that titanium enolates could be generated by reaction of biscyclopentadienyltitanium al-kylidene complexes and acyl halides [93]. Oshima and coworkers reported the formation of titanium enolates from a-iodoketones with allylsilane and titanium tetrachloride [94]. Mukaiyama and coworkers reported the generation of titanium enolates from a-bromoketones on treatment with TiCh and copper powder [95]. 

Nucleophilic substitution reaction is another class of important transformations that organosilicon reagents play key roles in organic synthesis. Electrophiles such as acyl and alkyl halides activated by a Lewis acid in a stoichiometric amount readily react with silyl enol ethers, allylsilanes, and alkenylsilanes. ... 

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