Olefin Hydroarylation Catalyzed by a Single-Component Cobalt(-I) Complex

Abstract

A single-component Co­(-I) catalyst, [(PPh3)3Co­(N2)]­Li­(THF)3, has been developed for olefin hydroarylations with (N-aryl)­aryl imine substrates. More than 40 examples were examined under mild reaction conditions to afford the desired alkyl-arene product in good to excellent yields. Catalysis occurs in a regioselective manner to afford exclusively branched products with styrene-derived substrates or linear products for aliphatic olefins. Electron-withdrawing functional groups (e.g., -F, -CF3, and -CO2Me) were tolerated under the reaction conditions.

Regioselective Mercury(I)/Palladium(II)-Catalyzed Single-Step Approach for the Synthesis of Imines and 2-Substituted Indoles

“…1 H NMR (500 MHz, CDCl 3 ): δ 2.28 (s, 3H, CH 3 -2’), 3.83 (s, 3H, CH 3 O), 6.73–6.78 (m, 2H, H-2), 6.91–6.95 (m, 2H, H-3), 7.72–7.75 (m, 2H, H-3”), 8.04–8.09 (m, 2H, H-2”). Signals attributed to 7b : 2.65 (s, CH 3 -2’), 3.74 (s, CH 3 O), 7.74–7.80 (m, H-3”) [ 100 ].…”

“…1 H NMR (600 MHz, CDCl 3 ): δ 2.22 (s, 3H, CH 3 -2’), 3.82 (s, 3H, CH 3 O-4), 3.86 (s, 3H, CH 3 O-4”), 6.72–6.76 (m, 2H, H-2), 6.88–6.92 (m, 2H, H-3), 6.93–6.96 (m, 2H, H-3”), 7.91–7.95 (m, 2H, H-2”). 13 C NMR (150 MHz, CDCl 3 ): δ 17.1 (C-2’), 55.4 ( CH 3 O-C4”), 55.5 ( CH 3 O-C4), 113.6 (C-3”), 114.2 (C-3), 120.9 (C-2), 128.7 (C-2”), 132.5 (C-1”), 145.0 (C-1), 155.8 (C-4), 161.4 (C4”), 164.8 (C-1’) [ 99 , 100 ].…”

Well-Defined Low-Valent Cobalt Complexes in Catalysis: An Overview

“…This complex was then applied in catalysis by Tilley in 2020 and 2021. 40,61 Co-20 was used as a well-defined catalyst for the C−H bond activation of aromatic imines with alkynes and alkenes as partners (Scheme 17b). 61 Rather than monodentate phosphines as ligands, Peters also synthesized in 2015 the Co(−I) complex Co-21 bearing the tetradentate ligand o-[( i Pr 2 P)C 6 H 4 ] 3 B (TPB).…”

“…40,61 Co-20 was used as a well-defined catalyst for the C−H bond activation of aromatic imines with alkynes and alkenes as partners (Scheme 17b). 61 Rather than monodentate phosphines as ligands, Peters also synthesized in 2015 the Co(−I) complex Co-21 bearing the tetradentate ligand o-[( i Pr 2 P)C 6 H 4 ] 3 B (TPB). 62a Starting from the Co(0) complex Co-22 62b in the presence of NaC 10 H 8 and 12-crown-4, Co-21 could be isolated and fully characterized, including an X-ray structure (Scheme 18a).…”

C–H Activation by Isolable Cationic Bis(phosphine) Cobalt(III) Metallacycles

“…Stoichiometric studies by Klein using Co­(Me)­(PMe 3 ) 4 established that a neutral cobalt­(I) complex mediates facile cyclometallation reactions likely proceeding by C–H oxidative addition followed by reductive elimination of methane. More recently, cobalt-catalyzed hydroarylation reactions using reduced Co(0) and Co­(−I) precatalysts, Co­(PMe 3 ) 4 and [Co­(PPh 3 ) 3 (N 2 )]­[Li], have been reported and concerted ligand-to-ligand hydrogen transfer of the arene C–H bond to the unsaturated coupling partner with concomitant 2-electron oxidation of the cobalt center was proposed. Additionally, redox-neutral concerted metalation-deprotonation (CMD) by cobalt­(III) complexes has been frequently invoked with [C 5 Me 5 ]-ligated cobalt­(III) precatalysts in the presence of carboxylate additives .…”