Alkynes haloarenes, reaction with

Transition-metal-mediated C—X bond formation by intramolecular reactions with alkynes is a powerful strategy for the construction of heteroarene rings such as pyridines, pyrroles, and furans. Because of the wide availability of Sonogashira coupling of various haloarenes with terminal alkynes, these transformations provide efficient routes to synthesize fused heteroarenes, including isoquinolines, indoles, and benzofurans. In this chapter the construction of aromatic rings by transition-metal-catalyzed or transition-metal-mediated intramolecular C—X bond formation between C—X or X—H and alkynes is described. As shown in Scheme 19.1, Section... 

The palladium(II)-catalyzed reaction of haloarenes with alkenes and alkynes (Heck-type reactions) in aqueous media has become known only in the preceding few years [Eq. (14)]. 

Oxidative addition of aryl (or vinyl) halide to Pd(0) precursor forms the monoarylpalladium complex that is the common intermediate in the catalytic cross-coupling reactions of haloarene with organometallic compounds of main group elements such as Mg, Si, and Sn. Alkynylcopper, formed from alkyne, Cu(I) salt and base in the reaction mixture, transfers the ligand to the above Pd complex, giving an intermediate complex with aryl (or vinyl) and alkynyl ligands bonded to Pd. Reductive elimination of arylacetylene (or enyne) occurs... 

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