N-heterocyclic carbene–palladium catalysts for the bisdiene cyclization-trapping reaction with sulfonamides under thermal and microwave conditions

Simple palladium-N-heterocyclic carbene catalysts readily effect the palladium-catalyzed cyclization-trapping of bisdienes with sulfonamides. The reaction is quite efficient for a variety of sulfonamides and several bisdienes. For example, using 0.1% of the in situ generated or preformed (IMes)Pd(η3-C3H5)Cl complex, the cyclization-trapping of a simple bisdiene with TsN(H)CH2Ph proceeds in good yield under thermal conditions (74–75%, 75 °C, 9 h). The same reaction run under microwave irradiation proceeds somewhat faster and in even higher yield (86%, 75 °C, 2.5 h).