Missing cyclization pathways and new rearrangements unveiled in the gold(I) and platinum(II)-catalyzed cyclization of 1,6-enynes

Cyclopropyl metal carbenes formed in the 6-endo-dig cyclization may evolve to form seven-membered ring intermediates. This has been achieved for the first time by using highly electrophilic platinum(II) and gold(I) complexes. Gold(I) also triggers a remarkable rearrangement of certain enynes leading to complex cyclic systems. A new cationic platinacycle is described, which catalyzes skeletal rear-rangements and other reactions of enynes at room temperature. (c) 2007 Elsevier Ltd. All rights reserved.