Allylic Rearrangements. XX. Some Addition Reactions of Butenylmagnesium Bromide

Preceding studies of the butenyl Grignard reagent have indicated a striking tendency on the part of the reagent to introduce an α-methylallyl group in coupling reactions with allylic chlorides and in addition reactions to aldehyde, ketones and carbon dioxide. Even with highly-hindered ketones as diisopropyl ketone and acetomesitylene the reaction products are predominantly α-methylallyl derivatives. have now turned to the investigation of other types of addition reactions of butenylmagnesium bromide and find that with phenyl isocyanate, ethyl formate arid ethyl orthoformate the reaction products correspond almost exclusively to the secondary form of the Grignard reagent. With ethyl orthoformate some ( <4%) of the diethyl acetal of 3-pentenal was obtained but in the other reactions none of the products resulting from the introduction of the primary butenyl group by the Grignard reagent was detected.