Selective synthesis of 2-pyridones and pyrimidine-2,4-diones by neutral rhodium(I) complex-catalyzed cyclocotrimerization of alkynes and isocyanates

A neutral rhodium(I) complex, 'RhCI(PPh3)(2)' generated by the combination of [RhCl(C2H4)(2)](2) with a fourfold amount of PPh3, effectively catalyzed the cyclocotrimerization of alkynes (1) and isocyanates (2) to give 2-pyridones (3) and/or pyrimidine-2,4-diones (4), selectively, by controlling the molar ratio of alkynes (1) and isocyanates (2). (c) 2006 Elsevier Ltd. All rights reserved.