In situ generation of highly active bis(N-heterocyclic) carbene palladium as an efficient catalyst in direct S-arylation of methylphenyl sulfoxide and the Heck reaction: Ligand steric effects in product selectivity

The use of 1,3-bis(N-heterocyclic) carbene ligands with different alkyl wingtip groups (alkyl = methyl, isopropyl and tert-butyl) is an effective method for the palladium-catalysed direct S-arylation of methylphenyl sulfoxide and C-C coupling of various of aryl halides with alkenes. The reactions proceed in moderate to good yields. Interestingly, it is shown experimentally that, by using bulkier bidentate N-heterocyclic carbene ligands, more selective catalytic systems towards cis products in Heck coupling reactions can be achieved.