Inter-intramolecular alkenyl-alkene coupling

Scheme 3-37 Inter-intramolecular alkenyl-alkene coupling cascades involving C H activation on an alkene and arene, respectively [188d,e]. A = Pd(OAc), K2CO3, Bu NBr, DMF, 80 °C.

Scheme 8.49 Inter-intramolecular alkenyl-alkene and aryl-alkene coupling cascades involving C-H activation [1 1 5, 357d,e], A Pd(OAc)j, KjCOj, riBu NBr, DMF, 80°C, 24h. B Like A, but, 100°C for 7 and 21 days, respectively [115],...

Whether the reaction is inter- or intramolecular, the Heck reaction generates vinyl(hetero)arenes or dienes from an alkene and a (hetero)aryl or alkenyl halide [130]. This reaction has great versatility and is applicable to a wide range of aryl and alkene species. Mechanistically, the Heck reaction varies from that depicted in Fig. 4.3. While the oxidative addition of the halogen species occurs, the transmetalation step is replaced by the coordination of the alkene. This is followed by a migratory insertion which essentially substitutes for the cross-coupling step. The product is released not by a reductive elimination, but by a 3-hydride elimination sequence (Fig. 4.5). 

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