Pd-catalyzed Heck cyclization and in situ hydrocarboxylation or hydromethenylation via a hydrogen borrowing strategy

A Pd-catalyzed hydrocarboxylation of the in situ formed neopentylic alkenes by the use of borrowed hydrogen from Heck-type beta-hydride elimination was reported. The advantage of this strategy is that no additional hydrogen sources or organometallic reagents were required. It was found that CHCl3 was not only used as a safe and convenient CO source but also proved superior in the linear/branched selectivity over carbon monoxide. Furthermore, the in situ formed neopentylic alkenes could be chemoselectively functionalized with other C-C unsaturated bonds being unchanged, even the less sterically hindered ones.