Contrasted effect of CO on the metal-catalyzed cycloisomerization of O-tethered enynes derived from monoterpenes

The CO-bubbling effect in cycloisomerization reactions of enynes derived from monoterpenes has been studied using PtCl2, [Rh2Cl2(CO)(4)] and AuCl3 as catalytic systems. All the precursors are efficient catalysts for the cycloisomerization of O-tethered enynes. The reaction proceeds through exo-dig and endo-dig pathways, which are consistent with the exclusive coordination of the alkyne triple bond to the metal center. The CO ligand not only increases the reaction rates but also induces significant variations in the two reaction pathways. Notably, this effect is also strongly dependent on the nature of the starting enyne. Copyright (C) 2011 John Wiley & Sons, Ltd.