Trimethylsilyl tribromoacetate

Dibromoketene. The reaction of trimethylsilyl tribromoacetate (l) with triphenylphosphine in the presence of excess cyclopentadiene gives the cycloaddition product, 7,7-dibromobicyclo[3.2.0]hept-2-ene-6-one (2), in 89% yield. 

Dibromoketen can be generated from the reaction of trimethylsilyl tribromoacetate and triphenylphosphine. The isolated product (58) is derived from reaction with the cyclopentadiene solvent. 

Dibromoketene can be generated from trimethylsilyl tribromoacetate (28) on treatment with Ph3P. Many other trihaloacetic acid derivatives undergo similar dehalogenation reactions. 

Trimethylsilyl tribromoacetate allowed to react at 0° with the equimolar amount of triphenylphosphine and excess cyclopentadiene in toluene 7,7-dibromo-bicyclo[3.2.0]hept-2-en-6-one. Y 89%. F. reaction s. T. Okada and R. Okawara, Tetrah. Let. 1971, 2801. 

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