Novel 1,3-dipolar cycloadditions of fulvenes and hydrazonyl chlorides: a facile synthesis of the cyclopenta[d]pyridazines

A simple and convenient route for one-pot synthesis of cyclopenta[d]pyridazine through 1,3-dipolar cycloaddition of fulvenes and hydrazonyl chlorides is described. The reaction of fulvenes with hydrazonyl chlorides in the presence of silver carbonate smoothly afforded a series of cyclopenta[d]pyridazines.