Multi-component syntheses of heterocycles initiated by palladium catalyzed generation of alkynones and chalcones

Alkynones and chalcones are important three-carbon building blocks in heterocyclic chemistry. They can be very efficiently generated by palladium-copper catalyzed reactions. Ynones are generated from acid chlorides and terminal alkynes in the sense of a cross-coupling reaction, and chalcones are formed from (hetero)aryl halides and propargyl alcohols in the sense of a coupling-isomerization sequence. Considering the mild reaction conditions of Sonogashira coupling this is an entry to sequential and consecutive transformations opening new diversity oriented routes to heterocycles, such as furans, 3-halofurans, pyrroles, pyrazoles, substituted and annelated pyridines, pyridimines, benzoheteroazepines, and tetrohydro-b-carbolines, by consecutive coupling-cyclocondensation or coupling-isomerization-cyclocondensation sequences.