Multi-component Heterocycle Syntheses via Catalytic Generation of Alkynones

Alkynones are versatile three-carbon building blocks in heterocyclic chemistry. They are easily and efficiently prepared by a modified Sonogashira coupling of acid chlorides and terminal alkynes. As a consequence of the mild reaction conditions the stage is set for new diversity-oriented routes to heterocycles by sequential and consecutive transformations. Hence, isoxazoles, indolizines, pyrazoles, pyridimines, 1,5-benzoheteroazepines, furans, oxazoles, pyrroles, tetrahydro- β-carbolines, 4H-thiochromen-4-ones and 4H-thiopyrano[2,3-b]pyridin-4-ones are readily accessible by multicomponent coupling-cycloaddition, coupling-addition-cyclocondensation, or coupling-addition-substitution reactions in a one-pot fashion.