不飽和酸エステルとブロムアセトニトリルとのラジカル反応

概要

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Authors studied the reactions of methyl crotonate and methyl vinylacetate with bromoacetonitrile at 120-150°C using di-tert-butylperoxide as initiator. Methyl - γ -bromocrotonate and methyl- α -bromo- β -methyl- γ -cyanobutyrate were the main products in the reaction of methyl crotonate. In case of the reaction of methyl vinylacetate, the corresponding compound (α -bromovinylacetate) was not obtained. The formation of γ -bromocrotonate in the latter case could be explained as the rearrangement of the intermediate radical CH2=CH-CHCO2CH3 into ·CH2-CH=CH-CO2CH3. Apparent activation energy of the hydrogen abstraction reaction from methyl crotonate calculated from the rate of formation of methyl- γ -bromocrotonate was lower than that from methyl vinylacetate, and apparent activation energy of the addition of bromoacetonitrile to the former was higher than that of the latter. Conjugative stabilization of intermediate radical plays an important role in theae reactions. The effect of addition of palladium chloride and of other heavy metal salts on the hydrogen ahstraction and on the addition reaction of BrCH2CN was also studied.