N-Substituted 2-Aminobiphenylpalladium Methanesulfonate Precatalysts and Their Use in C–C and C–N Cross-Couplings

Abstract

A series of phosphine-ligated palladium precatalysts based on N-methyl- and N-phenyl-2-aminobiphenyl have been developed. Substitution at the nitrogen center prevents the presence of traces of aminobiphenyls that contain a free −NH2 group from contaminating cross-coupling products. These precatalysts produce N-substituted carbazoles upon activation, which cannot consume starting materials. These precatalysts were efficiently generated from 2-aminobiphenyl with minimal purification and found to be highly effective in Suzuki–Miyaura and C–N cross-coupling reactions.

Oxidative Addition Complexes as Precatalysts for Cross-Coupling Reactions Requiring Extremely Bulky Biarylphosphine Ligands

“…To facilitate the use of these ligands, we have developed several generations of palladacyclic precatalysts ( G1 – G5 , Figure 1), which are able to accommodate a range of phosphine-based ligands. 5,6 These precatalysts can be used to promote cross-coupling reactions with high efficiency. This is due, in part, to the preassociation of the ligand with the Pd center and to the rapid formation of a L–Pd(0) species under the reaction conditions.…”

“…While G3 precatalysts containing these ligands are readily isolated, they form carbazole upon catalyst activation, which occasionally can cause inhibition of the catalyst based on kinetic and mechanistic studies. 5c,6a,8 Precatalysts of type G4 and G5 were prepared to address this, among other issues. However, G4 and G5 -based precatalysts based on L1 – L4 are only formed with difficulty.…”

Design, Synthesis, and Validation of an Effective, Reusable Silicon-Based Transfer Agent for Room-Temperature Pd-Catalyzed Cross-Coupling Reactions of Aryl and Heteroaryl Chlorides with Readily Available Aryl Lithium Reagents

“…Aiming to reduce catalyst loadings, we next turned to Buchwald’s recently developed palladium precatalysts, which form monoligated Pd(0) species in situ when exposed to base. 14 We reasoned that the alkoxide intermediate 3 would readily activate the precatalyst, thereby avoiding the need for an external base. Commercially available Buchwald G2 and G3 precatalysts led to incomplete conversions (entries 6 and 7).…”

“…Commercially available Buchwald G2 and G3 precatalysts led to incomplete conversions (entries 6 and 7). Pleasingly, however, when employing 3 mol % precatalyst G4 14c and 1.3 equiv of PhLi, the reaction now proceeded to full conversion in 24 h, at room temperature, to furnish 6a in near quantitative yield (98%) with excellent recovery of 1 (84%, entry 8). Importantly, 1 can be recovered and reused repeatedly without sacrificing reactivity.…”

Palladium‐Catalyzed C−H Arylation of α,β‐Unsaturated Imines: Catalyst‐Controlled Synthesis of Enamine and Allylic Amine Derivatives

“…Buchwald precatalysts [8b,c] facilitate catalyst generation, often lead to increased activity, and allow a lower ligand loading. Therefore, we employed Buchwald-type [11] precatalysts 6 and 7 (with L = NiXantphos; Table 1, entries 5 and 6). The use of precatalyst 7 led to the γ-arylated product 4ab in 85% AY with high selectivity (> 20:1).…”