Branch-Selective, Iridium-Catalyzed Hydroarylation of Monosubstituted Alkenes via a Cooperative Destabilization Strategy

Abstract

Highly branch-selective, carbonyl-directed hydroarylations of monosubstituted alkenes are described. The chemistry relies upon a cationic Ir(I) catalyst modified with an electron deficient, wide bite angle bisphosphine ligand. This work provides a regioisomeric alternative to the Murai hydroarylation protocol.

Transition metal-catalyzed ketone-directed or mediated C–H functionalization

“…31 The key for the inversion of the selectivity is the use of an electrondeficient bis-phosphine ligand (13), which can presumably accelerate the reductive elimination. In 2014, Bower and coworkers reported an alternative iridium-catalyzed system that is highly selective for branched products (Scheme 12).…”

Iridium(I)‐Catalyzed Intramolecular Hydrocarbonation of Alkenes: Efficient Access to Cyclic Systems Bearing Quaternary Stereocenters

“…[6] Moreover,w hile these processes allow to build products with tertiary stereocenters;the assembly of highly appealing quaternary carbon centers has not been demonstrated. [13] After screening different Rh I and Ir I species, [14] we found that the mixture of Ir(cod) 2 BArF (5 mol %) and the electron deficient diphosphine ligand d F ppe (5 mol %), [15] provides good yields of cyclopentane 2a ( Table 1, entry 1). [8] Regardless of the type of mechanism, almost all the above cases deal with the activation of aromatic and heteroaromatic C(sp 2 )ÀHb onds,r estricting the type of products that can be accessed.…”

Branch Selective Murai-type Alkene Hydroarylation Reactions

“…In 2014, our group reported a mechanistic framework to achieve this (Scheme 9A, cartoon representation). 23 Specifically, we envisaged that modification of the Ir-system with a wide-biteangle bisphosphine ligand would increase the bond angle y, which, in turn, would decrease the bond angle x a/b at the stage of 9a/9b. This pushes the alkyl ligands closer to the arene, such that the intermediates are destabilized and the rate of reductive elimination is enhanced.…”

“…To further increase the efficiency of the process, we prepared the novel electron-deficient bisphosphine d Further studies revealed that a variety of different carbonyl directing groups (amides, ketones) are effective, and hydroarylation of alkyl-and aryl-substituted alkenes can be achieved with high selectivity (Scheme 10). 23 Note that propylene gas allows the direct installation of challenging ortho-isopropyl groups. For substrates possessing substitution at C-3, orthoregioselectivity is determined by a combination of steric and electronic effects, with high selectivities often observed.…”