Cycloiridation of α,β-unsaturated ketones, esters, and acetophenone

C-H activation of acetophenone and cyclic and acyclic alpha,beta-unsaturated ketones or esters occurs with [IrH2(acetone)(2)(PPh3)(2)](+). In the case of acyclic alpha,beta-unsaturated ketones or esters, the beta-C-H bond was activated to afford iridafuran hydrides as cyclometalation products. For cyclopentenone, a cyclic alpha-,beta-unsaturated ketone, the C-H activation affords an eta(5)-hydroxycyclopentadienyl iridium hydride. The activation of the ortho C-H bonds in acetophenone affords orthometalated products structurally related to the iridafuran hydrides. Plausible mechanisms are proposed for reactions in each case. In particular, the formation of iridafurans is believed to proceed by a mechanism analogous to that previously proposed for the RuH2(CO)(PPh3)(3)-catalyzed Murai reaction.