Iridium(III) Catalysts with an Amide‐Pendant Cyclopentadienyl Ligand: Double Aromatic Homologation Reactions of Benzamides by Fourfold C−H Activation

Abstract

The synthesis, characterization, and catalytic performance of iridium(III) catalysts that bear an amide‐pendant cyclopentadienyl ligand ([CpAIrI2]2) is reported. These [CpAIrI2]2 catalysts were obtained from the complexation of a CpA ligand precursor with [Ir(cod)OAc]2 followed by oxidation. Double aromatic homologation reactions of benzamides with alkynes by fourfold C−H activation proceeded in good to high yield with these [CpAIrI2]2 catalysts, demonstrating their superior catalytic performance in this challenging transformation.

Multiple annulations of inert C(sp2)–H bonds with alkynes

“…78 Recently, Matsunaga and co-workers demonstrated Ir(III) catalyzed four-fold annulation of benzamides 135 with alkynes to provide enlarged aromatic homologation anthracene products 136 (Scheme 36). 79 Various amide-bearing cyclopentadienyl anchored Ir(III) catalysts were prepared and screened. Interestingly, the catalyst Ir-I was found to be suitable for providing densely substituted unusual anthracene derivatives in good yields.…”

Teaching cyclopentadienyl how to leave: a case study of the [CpIr(COD)Br]+ complex

“…In fact, the substitution of COD in half-sandwich complexes is typically used for the preparation of organometallic derivatives for catalytic studies. 11–17 It was shown later that this type of reactivity was observed for the pentamethylated analogue of 1 ( i.e. , [Cp*Ir(COD)Br] + ( 3 ) transforms into [Cp*Ir(P(OMe) 3 ) 2 Br] + ( 4 ) under the same conditions).…”

Chiral Carboxylic Acid Assisted Enantioselective C–H Activation with Achiral CpxMIII (M = Co, Rh, Ir) Catalysts

“…The broad opportunity to electronically modify the metal catalysts would be an advantage of CCA-assisted enantioselective C–H functionalization. Many studies on racemic reactions have demonstrated that electronic tuning of the Cp ligands leads to higher reactivity and unique chemoselectivity or site selectivity . The hybridization of such electronically tuned Cp ligands with CCAs could also represent another future direction to realize high reactivity/unique selectivity together with enantioselectivity.…”