Palladium-Catalyzed Vinylation of Haloazulenes and Halotropolones with Olefins. Utility of the Heck Reaction in the Conjugated Carbon Chain Preparation

The reactions of 3-iodotropolone with styrenes (styrene, p-methoxystyrene, and 2-vinylpyridine), methyl acrylate, and allylic compounds (methyl 3-butenoate, 3-butenenitrile, 1-allyl-3,4-dimethoxybenzene, and 1-allyl-3,4-methylenedioxybenzene) were carried out, according to the modified Heck’s procedure, to give 3-styryl-, 3-(2-carboxyvinyl)-, and 3-(3-substituted 1-propenyl)tropolones, respectively. Similarly, 4-bromo- or 5-bromotropolone was made to react with these olefins to yield 4-styryltropolone or the corresponding 5-(2-substituted vinyl)- and 5-(3-substituted 1-propenyl)tropolones. Substitution of 2-chlorotropone by styrenes produced 2-styryltropones. Extension of the vinylation to 2-amino-6-bromoazulenes, ethyl 3-bromo-1-azulenecarboxylate, and diethyl 2-chloro-1,3-azulenedicarboxylate resulted in a similar substitution.