New Insight into the Azaenamine Behaviour of N-Arylhydrazones: First Aldol and Improved Mannich Reactions with Unactivated Aldehydes

N-Arylhydrazones can be added to various aldehydes in amine solvents to form new Mannich and aldol products. A wide range of hydrazones and aldehydes formally reported as unreactive can now be coupled to give adducts easily converted into azoalkenes. These transformations parallel the aldolisation/crotonisation processes allowing access to novel heterocycles and the design of new multi-component reactions.