Novel and efficient synthesis of medium-sized heterocycles such as azepine, oxepine, and benzo[d]azocine derivatives is described. Treatment of bromoallenes having a nucleophilic moiety with sodiumalkoxide and a palladium(0) catalyst in the presence of an alcohol leads to regioselective formation of medium-sized rings at the central position of the allenic carbon.
We have developed a highly regio- and stereoselective synthesis of medium-sized heterocycles containing one or two heteroatoms via cyclization of bromoallenes bearing an oxygen, nitrogen, or carbon nucleophilic functionality in the presence of a palladium(0) catalyst and alcohol. In this reaction, bromoallenes act as an allyl dication equivalent, and the intramolecular nucleophilic attack takes place