Cu-Catalyzed Intermolecular γ-Site C–H Amination of Cyclohexenone Derivatives: The Benefit of Bifunctional Ligands

Abstract

Utilizing 1,10-phenanthroline-type bifunctional ligands, an efficient Cu-catalyzed intermolecular site-selective remote C−H amination using cyclohexenone derivatives and anilines was realized. The amide group installed on the bifunctional ligand played a key role in stabilizing the N-centered radical generated in situ to realize C−N-directed formation. Meanwhile, a useful catalytic system for site-selective intermolecular remote γ-C−H amination to p-aminophenols and γ-aminated enones was established. This economical and practical approach using oxygen as the terminal oxidant was mild and environmentally friendly.

A ligand-enabled, copper(ii)-catalyzed, highly selective and efficient synthesis of 2E-alkenylfurans from ynenones

“…Cu(OTf ) 2 first coordinates with L1 to afford the L1Cu(II) complex. The latter coordinates with ynenone 1 to give complex A, 9 ligand assists cleavage of α C-H bond to realize α-H 1,2migration and stabilizes the in situ-generated carbocation 12 to afford the complex C. Next, a general copper-elimination process to E-selective 2-alkenylfuran 2 occurs and releases the copper complex to the next catalytic cycle.…”

“…Recently, we developed an 1,10-phenanthroline-type bifunctional ligand by installing an amide group at the 3′-position of 2-phenyl-1,10-phenanthroline L1 to assist Cu( ii )-catalyzed intermolecular γ-site C–H amination. 12 Upon development of this type of ligand, several functional groups installed on 1,10-phenanthrolines L2–L7 were synthesized via a Pd-catalyzed Suzuki coupling reaction 13 (Table 1).…”

Cu‐catalyzed synthesis of 1‐naphthols with terminal alkynes and 2‐bromoaryl ketones

“…CuI first coordinates with Ln to afford the LnCu(I) complex A, [12] which further reacts with phenylacetylene 1a to afford the LnCu(I) complex B. [13] Then, the halide exchange between 2a and NaI proceed to form 2a', [14] and the LnCu(I) complex B undergoes oxidative addition reaction with the help of direct group carbonyl of 2a' to give alkynyl copper(III) C, [15] which subsequently experiences reductive elimination to produce D. Assisted by base and ligand, the keto-enol tautomerization of D is realized to afford intermediate E. [7,16] The subsequent 6-endo-dig cyclization is performed to give intermediate F. Finally, the intermediate F undergoes dehydration to deliver T A B L E 2 Substrate scope a a Reaction conditions unless stated otherwise: 1 (0.20 mmol, 1.0 equiv), 2 (0.40 mmol, 2.0 equiv), NaOH (0.40 mmol, 2.0 equiv), NaI (0.40 mmol, 2.0 equiv), CuI (10 mol%), and L6 (20 mol%) in solvent (1 mL) at 120 C under N 2 for 24 h. Isolated yields.…”

“…Assisted by base and ligand, the keto–enol tautomerization of D is realized to afford intermediate E . [ 7,16 ] The subsequent 6‐endo‐dig cyclization is performed to give intermediate F . Finally, the intermediate F undergoes dehydration to deliver product 3a and releases the Ln Cu(I) complex simultaneously.…”

Catalyst- and additive-free [3 + 3] cyclization–aromatization of β,γ-dioxobutanoate with amines for synthesis ofp-aminophenols

“…14 Because of their versatile structures, the synthesis of p -aminophenols has received considerable attention. However, methods for their synthesis from p -nitrophenols, 15 p -halophenols or p -haloanilines, 16 phenols or anilines 17 suffer from obvious drawbacks, namely multistep synthesis processes, harsh reaction conditions, and the need for expensive catalysts, oxidants and acids.…”