Copper-catalyzed tandem A3-coupling-isomerization-hydrolysis reactions of aldehydes and terminal alkynes leading to chalcones

Catalyzed by a simple copper salt, the reaction of an aryl aldehyde and a terminal alkyne in the presence of piperidine delivers the valuable chalcone products, which were rarely found in previous A(3) coupling reactions. This reaction can be applied to a wide range of substrates. Mechanistic studies indicate that this reaction experiences a tandem process containing A(3) coupling, copper assisted isomerization of propadienamine to allenylamine and subsequent hydrolysis.