Iridium(III)-Catalyzed Branch-Selective C–H Alkenylation of Aniline Derivatives with Alkenes

Abstract

The branch-selective C−H alkenylation with alkenes using an iridium catalyst is reported. The Ir(III)-catalyzed reaction of aniline derivatives that contain a pyrimidine-directing group with vinylsilanes and terminal aliphatic alkenes results in branch-selective C−H alkenylation. The reaction provides a broad substrate scope for aniline derivatives, and a variety of functional groups are tolerated. Density functional theory calculations were performed in an attempt to understand the origin of the branch selectivity.

An Unusual Perpendicular Metallacycle Intermediate is the Origin of Branch Selectivity in the Rh(II)-Catalyzed C–H Alkylation of Aryl Sulfonamides with Vinylsilanes

“…This trend is in agreement with experimental results that indicate that a branched product is preferably obtained. The origin of this rare branch selectivity arises from the steric repulsion between the TMS group and the equatorial acetic acid ligand on the nonparticipating rhodium atom (Figure A) . In the linear-selective migratory insertion TSs, the TMS group is closer to the methyl group of the acetic acid ligand, which forces the ligand to adopt a distorted form compared to the preferred linear coordination.…”

Rh(III)-Catalyzed [3 + 2] Annulation of Aniline Derivatives with Vinylsilanes via C–H Activation/Alkene Cyclization: Access to Highly Regioselective Indoline Derivatives

“…We recently reported a branch-selective C−H alkenylation of anilines with vinylsilanes using [Cp*IrCl 2 ] 2 as a catalyst that involved the regioselective migratory insertion of a vinylsilane into a C−Ir bond and is governed by the strain energy resulting from steric repulsion between a silyl group and the Cp* ligand. 20 Taking advantage of this protocol, we found that the Rh(III)-catalyzed C−H activation/alkene cyclization of aniline derivatives with vinylsilanes provides highly regioselective C3-substituted indo-…”

Transition‐Metal‐Catalyzed, Chelation‐Assisted C−H Alkenylation and Allylation of Organic Molecules with Unactivated Alkenes

“…The optimal conditions combine [Cp*IrCl 2 ] 2 (5 mol %) as a catalyst, AgSbF 6 (20 mol %) as an additive, and a stoichiometric amount of Ag 2 CO 3 as an oxidant in 1,2‐dichloroethane as a solvent at 80 °C for 4 h under a nitrogen atmosphere (Scheme 35). [40] A wide range of differently substituted anilines ( 61 ) possessing electron‐withdrawing as well as electron‐donating substituents were all smoothly coupled with vinyl silanes, providing the alkenylated product in good to moderate yields. In the case of meta ‐substituted anilines, the alkenylation exclusively occurred at the less hindered position.…”

“…In the proposed mechanism, the reaction initiated from the coordination of ( 61 g ) to the Ir(III) complex followed by the ortho C−H bond activation generates the metallacycle intermediate ( E5 ) (Scheme 36). [40] The metallacycle intermediate (E5 ) also directly formed from the [Cp*IrCl 2 ] 2 under the catalytic condition. Then, coordination of alkene with metallacycle intermediate ( F5) and subsequent insertion between the Ir−C bond produces the eight‐membered metallacycle ( G5 ).…”