Copper(I) Complexes of Amide Functionalized Bisphosphine: Proximity Enhanced Metal–Ligand Cooperativity and Its Catalytic Advantage in C(sp³)–H Bond Activation of Unactivated Cycloalkanes in Dehydrogenative Carboxylation Reactions

CuI-amidobis(phosphine) catalyzed C(sp3)–C(sp3) direct homo- and hetero-coupling of unactivated alkanes via C(sp3)–H activation

“…Previously, we reported the halogen-free copper( i )–amidobis(phosphine) complex [Cu{Ph 2 PC 6 H 4 C(O)NC 6 H 4 PPh 2 - o }] 2 (here onwards referred to as [PNP–Cu] 2 ) catalyzed C(sp 3 )–H bond activation of unactivated cycloalkanes via oxidative dehydrogenative carboxylation (ODC) reactions, which proceeded through a radical mechanism. 13…”

“…Substrates such as pyridine ( xvii ) and nitro ( xviii )-based benzyl alkanes did not show conversions, possibly due to the coordination of the substrate to form a stable complex with the catalyst, as observed previously. 13…”

“…As per the calculations, the addition of tert -butanol across the Cu–N bond in [Cu I (PNP)] to form intermediate B was found to be roughly ergoneutral, which highlights the bifunctional capability of the Cu–N moiety in [Cu I (PNP)] for activating C–H bonds. 13…”

“…87 kcal mol −1 based on isodesmic hydrogen atom transfer (HAT) free energy () calculations. 13 Therefore, despite H-atom transfer from [Cu I PNHP] to the tert -butoxy radical being energetically favourable, the overall transformation to form D is slightly endergonic due to the energy needed to generate two equivalents of the tert -butoxy radical from DTBP.…”

CuI–Amidobis(phosphine)-Catalyzed Direct Amidation of Unactivated Alkanes via C(sp3)–H Activation

“…The amidation of unactivated alkanes using halide-based Fe II , Co II , and Cu II catalysts via a radical mechanism is shown in Figure A: (a) FeCl 2 /NBS catalyzed amidation of only secondary C­(sp 3 )–H benzyl alkanes with benzamide, (b) CuCl/ t BuOK-mediated amidation of C­(sp 3 )–H alkanes via a radical pathway with benzamide, and (c) CoBr 2 /acetic acid-mediated amidation of only secondary C­(sp 3 )–H benzyl alkanes with sulfonamide. ,, These methods employed solvents, strong acid and base, and 5–10 mol % catalysts, and the yields were low to moderate. Recently we reported Cu I -catalyzed ([PNP-Cu] 2 ) oxidative dehydrogenative carboxylation of cycloalkanes to form allylic esters of aromatic and aliphatic carboxylic acids in good to excellent yield . The same catalyst also showed excellent catalytic activity toward homo- and heterocoupling of cycloalkanes.…”