ortho‐(Dimesitylboryl)phenylphosphines: Positive Boryl Effect in the Palladium‐Catalyzed Suzuki–Miyaura Coupling of 2‐Chloropyridines

Abstract

Catalytic systems combining ortho-(dimesitylboryl)phenylphosphines and palladium precursors have been evaluated in the Suzuki-Miyaura couplings of chloro-N-heterocycles, in particular 2-chloroA C H T U N G T R E N N U N G pyridines, with arylboronic acids. The Lewis basic character of the substrates does not interfere with the Lewis acidic site of the ligands, even for a substrate featuring free NH 2 groups. The influence of several reaction parameters has been studied and the ortho-dimesitylboryl moiety was actually found to substantially enhance the catalytic performance. The role of this group has been examined using preformed phosphine-borane/Pd complexes and the formation of an original phosphine/h 4 -boratabutadiene complex has been identified as a possible deactivation pathway. Regioselective coupling of 2,6-dichloro-3-nitropyridine with phosphine-borane/Pd catalysts has also been explored, and sequential double cross-couplings were found to give a direct and efficient access to unsymmetrical 2,6-diarylpyridines.

Oxidative‐Insertion Reactivity Across a Geometrically Constrained Metal→Borane Interaction

“…Notably, LZ‐type borane‐containing ambiphiles, which contain only a single pendant donor and could ostensibly foster a more sterically accessible M→BR 3 unit, have previously shown limited ability in promoting significant interactions between the metal and boron centers . However, we recently reported the singly buttressed platinum‐borane complex [Pt(κ 2 ‐ N,B ‐ Cy2 BIM)(CNAr Dipp2 )] ( 1 ), which features a bidentate (boryl)iminomethane (BIM) ligand .…”

“…[25][26][27][28][29][30][31][32] However,w er ecently reported the singly buttressed platinum-borane complex [Pt(k 2 -N,B-Cy2 BIM)(CNAr Dipp2 )] (1), which features ab identate (boryl)iminomethane (BIM) ligand. [25][26][27][28][29][30][31][32] However,w er ecently reported the singly buttressed platinum-borane complex [Pt(k 2 -N,B-Cy2 BIM)(CNAr Dipp2 )] (1), which features ab identate (boryl)iminomethane (BIM) ligand.…”

Chloro({2-[mesityl(quinolin-8-yl-κN)boryl]-3,5-dimethyl-phenyl}methyl-κC)palladium(II) as a Catalyst for Heck Reactions

“…Recently, Bourissou and coworkers demonstrated Suzuki–Miyaura couplings were catalyzed by mixtures of Pd(OAc) 2 , [PdCl 2 (COD)], Pd 2 (dba) 3 , or [Pd(ma)(nbd)] (nbd = norborna-1,4-diene, ma = maleic anhydride) with Ph 2 P( o -C 6 H 4 )BMes 2 [41,42]. Interestingly, the product formed from the reaction of [Pd(ma)(nbd)] with the monophosphine-borane was isolated and well characterized as [Ph 2 P( o -C 6 H 4 )BMes 2 ]Pd(ma) ( 7 ) (Scheme 3).…”

“…The preformed complex was shown to be a highly active Suzuki-Miyaura catalyst [41]. Interestingly, 7 was shown to oxidize in the presence of iodobenzene (Scheme 3) to form an η 4 -boratabutadiene iodophosphinopalladium(II) complex ( 8 ) [42]. The structure of 8 is very similar to that of 9 (Figure 2) reported by our group, which formed upon reaction of 8-(BMes 2 )quinoline with [PdCl 2 (PhCN) 2 ] [43].…”

Oxidative‐Insertion Reactivity Across a Geometrically Constrained Metal→Borane Interaction

“…Notably, LZ-type borane-containing ambiphiles, which contain only a single pendant donor and could ostensibly foster a more sterically accessible MBR 3 unit, have previously shown limited ability to promote significant interactions between the metal and boron centers. [25][26][27][28][29][30][31][32] However, we recently reported the singly-buttressed platinum-borane complex Pt( 2 -N,B-Cy2 BIM)(CNAr Dipp2 ) (1), which features a bidentate (boryl)iminomethane (BIM) ligand. [33] The constrained topology of the BIM framework enforces an acute and rigid B-C-N biteangle that contributes to a robust reverse-dative interaction between the Pt and B centers despite the presence of only a single L-donor buttress.…”