Silyl enol ethers with primary bromides

Secondary benzylic bromides, allylic bromides, and a-chloro ethers can undergo analogous reactions with the use of ZnBr2 as the catalyst.1 2 Primary iodides react with silyl enol ethers in the presence of Ag02CCF3.3... 

In the presence of a Lewis acid, silyl enol ethers can be alkylated with reactive secondary halides, such as substituted benzyl halides, and with chloromethylphenyl sulfide (ClCH2SPh), an activated primary halide. Thus, reaction of the benzyl chloride 10 in the presence of zinc bromide with the trimethylsilyl enol ether derived from mesityl oxide allowed a short and efficient route to the sesquiterpene ( )-ar-turmerone (1.22). Reaction of ClCH2SPh with the trimethylsilyl enol ethers of lactones in the presence of zinc bromide, followed by 5-oxidation and pyrolytic ehmination of the resulting sulfoxide (see Section 2.2), provides a good route to the a-methylene lactone unit common in many cytotoxic sesquiterpenes (1.23). Desulfurization with Raney nickel, instead of oxidation and elimination, affords the a-methyl (or a-alkyl starting with RCH(Cl)SPh) derivatives. ... 

Reaction of hindered trialkylsilyl ethers with Ph3PBr2 in CH2CI2 at rt affords primary and secondary alkyl bromides in excellent yield (70-94%) the reaction is valuable in the p-lactam field. The reaction rate is increased by addition of a catalytic amount of Zinc Bromide. Silylated enol ethers, such as trimethylsilyl(l-phenylvinyloxy)silane, provide vinyl bromides such as a-bromostyrene with Ph3PBr2 in refluxing CCL... 

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