Hydrochloric Acid → Ethyl 3-(2,2-dibromovinyl)-2,2-dimethylcyclopropanecarboxylate

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Reaction Steps

To a solution of ethyl 3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylate (14.81 g, 0.0625 mole) in 30 ml of ethylene bromide was added dropwise at 0° a solution of aluminum bromide (25 g, 0.094 mole) in 20 ml of ethylene bromide. After stirring for 41/2 hours, the solution was poured into a mixture of ice and water. The resultant mixture was extracted three times with ether. The ether extracts were combined and successively washed twice with water, twice with aqueous sodium bicarbonate, twice with aqueous sodium chloride, and then dried over anhydrous magnesium sulfate. The ether was then removed by evaporation, leaving a residue. The residue was dissolved in n-hexane, and 1,5-diazabicyclo[5.4.0] undec-5-ene was added to the solution. Dimethylformamide was added as a cosolvent. The solution was poured into dilute aqueous hydrochloric acid at 0°. The resultant mixture was extracted with ether. The ether extract was washed with water, aqueous sodium bicarbonate, aqueous sodium chloride, and then dried. The ether was removed, and the residue was distilled under reduced pressure to afford ethyl 3-(2,2-dibromovinyl)-2,2-dimethylcyclopropanecarboxylate (16.28 g, 87% yield); bp, 104-106°/0.28 mm.

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