Copper-catalyzed Oxidative Coupling Research Articles

ChemInform Abstract: Copper‐Catalyzed Oxidative N—S Bond Formation for the Synthesis of N‐Sulfenylimines.

Despite the remarkable success of the copper-catalyzed oxidative coupling reaction, direct cross-coupling of amines and thiols for the synthesis of N-sulfenylimines has not been previously reported. Using commercially available copper catalysts (CuI) and oxygen as an environmentally benign oxidant, synthetically useful N-sulfenylimines were prepared from amines and thiols in good yields without overoxidation of sulfur atoms.

Copper-catalyzed oxidative N-S bond formation for the synthesis of N-sulfenylimines.

Despite the remarkable success of the copper-catalyzed oxidative coupling reaction, direct cross-coupling of amines and thiols for the synthesis of N-sulfenylimines has not been previously reported. Using commercially available copper catalysts (CuI) and oxygen as an environmentally benign oxidant, synthetically useful N-sulfenylimines were prepared from amines and thiols in good yields without overoxidation of sulfur atoms.

Copper-catalyzed selective C_O bond formation by oxidative α-C(sp3)_H/O_H coupling between ethers and salicylaldehydes

Copper-catalyzed oxidative coupling of ethers and salicylaldehydes, via the direct α-C(sp3)–H bond functionalization of ethers in the presence tert-butyl hydroperoxide as an oxidant has been explored. The corresponding acetals were selectively formed in moderate to excellent yields. The sensitive formyl group of salicylaldehydes remained intact despite the oxidative reaction conditions.

In-depth structure–selectivity investigations on asymmetric, copper-catalyzed oxidative biaryl coupling in the presence of 5-cis-substituted prolinamines

Copper complexes of 5-cis-substituted prolinamines provided up to 87% ee in the enantioselective oxidative biaryl coupling of 3-hydroxy-2-naphthoates.

Copper-catalyzed oxidative coupling of acids with alkanes involving dehydrogenation: facile access to allylic esters and alkylalkenes.

We here describe a new copper-catalyzed oxidative coupling of acids with alkanes for the selective synthesis of allylic esters and alkylalkenes. This method achieves multiple dehydrogenation and esterification, representing a new unactivated C(sp(3))-H oxidative esterification of acids with common alkanes.

Copper-catalyzed oxidative coupling reaction of α,β-unsaturated aldehydes with amidines: synthesis of 1,2,4-trisubstituted-1H-imidazole-5-carbaldehydes

A convenient synthesis of 1,2,4-trisubstituted-1H-imidazole-5-carbaldehydes was developed, which features high atom economy, cheap catalysts and mild conditions.

Site-specific indolation of proline-based peptides via copper(II)-catalyzed oxidative coupling of tertiary amine N-oxides.

The first site-specific and purely chemical method for modifying proline-based peptides was developed via a convenient, copper-catalyzed oxidative coupling of tertiary amine N-oxides with indoles. This novel approach features high regioselectivity and diastereoselectivity, mild conditions, and compatibility with various functional groups. In addition, a simplified process was realized in one pot and two steps via in situ oxidative coupling of tertiary amine and indoles.

Reaction progress kinetic analysis of a copper-catalyzed aerobic oxidative coupling reaction with N-phenyl tetrahydroisoquinoline.

The results from a kinetic investigation of a Cu-catalyzed oxidative coupling reaction between N-phenyl tetrahydroisoquinoline and a silyl enol ether using elemental oxygen as oxidant are presented. By using reaction progress kinetic analysis as an evaluation method for the obtained data, we discovered information regarding the reaction order of the substrates and catalysts. Based on this information and some additional experiments, a refined model for the initial oxidative activation of the amine substrate and the activation of the nucleophile by the catalyst was developed. The mechanistic information also helped to understand why silyl nucleophiles have previously failed in a related Cu-catalyzed reaction using tert-butyl hydroperoxide as oxidant and how to overcome this limitation.

ChemInform Abstract: Oxidative Dehydrogenative Couplings of Pyrazol‐5‐amines Selectively Forming Azopyrroles.

AbstractNew protocols for the preparation of azopyrazoles are developed.

Synthesis of α-Ketoamides from Aryl Methyl Ketones and N,N-Dimethylformamide via Copper-Catalyzed Aerobic Oxidative Coupling

A copper-catalyzed aerobic oxidative coupling of aryl methyl ketones with <i>N</i>,<i>N</i>-dimethylformamide was developed, which afforded α-ketoamides by a sequence of dioxygen activation, C–H bond functionalization, and amide formation with <i>N</i>,<i>N</i>-dimethylformamide as the nitrogen source. Molecular oxygen was found to play a crucial role in this transformation.

Copper-catalyzed oxidative C-O bond formation of 2-acyl phenols and 1,3-dicarbonyl compounds with ethers: direct access to phenol esters and enol esters.

A copper-catalyzed oxidative coupling of 2-carbonyl-substituted phenols and 1,3-dicarbonyl compounds with a wide range of dibenzyl or dialkyl ethers is described. This protocol provides an efficient preparation of phenol esters and enol esters in good yields with high chemoselectivity. This method represents an alternative protocol for classical esterification reactions.

Oxidative dehydrogenative couplings of pyrazol-5-amines selectively forming azopyrroles.

New oxidative dehydrogenative couplings of pyrazol-5-amines for the selective synthesis of azopyrrole derivatives have been described. The former reaction simultaneously installs C–I and N–N bonds through iodination and oxidation, whereas the latter involved a copper-catalyzed oxidative coupling process. The resulting iodo-substituted azopyrroles were employed by treatment with various terminal alkynes through Sonogashira cross-coupling leading to new azo compounds.

Copper-Catalyzed Oxidative Coupling of Formamides with Salicylaldehydes: Synthesis of Carbamates in the Presence of a Sensitive Aldehyde Group

A diverse library of novel carbamates was synthesized utilizing copper-catalyzed oxidative C-O coupling of formamides and salicylaldehydes. Sensitive aldehyde groups remained intact in the presence of an oxidant and a transition-metal salt. Salicylaldehydes bearing electron-donating, electron-withdrawing, and halogen groups as well as 1-hydroxy-2-naphthaldehydes provided the desired carbamates in good to excellent yields.

Copper-Catalyzed Aerobic Oxidative Coupling of Aromatic Alcohols and Acetonitrile to β-Ketonitriles

A practical, convenient, and cheap copper-catalyzed aerobic oxidative coupling of aromatic alcohols and acetonitrile to β-ketonitriles has been developed. The green C-C bond formation involving the loss of two hydrogen atoms from the corresponding two carbons, respectively, unlocks opportunities for markedly different synthetic strategies.

A Cu-catalyzed practical approach to α-ketoesters under air: an efficient aerobic oxidative dehydrogenative coupling of alcohols and α-carbonyl aldehydes

A novel and efficient approach to α-ketoesters has been developed with wide functional group tolerance. This copper-catalyzed oxidative dehydrogenative coupling reaction of alcohols and α-carbonyl aldehydes employs air as the oxidant and generates H2O as the only by-product. Broad substrate scope, high atom economy and mild reaction conditions make this chemistry very practical.

Copper-catalyzed oxidative cascade coupling of N-alkyl-N-phenylacrylamides with aryl aldehydes

An oxidative cascade coupling reaction between N-alkyl-N-phenylacrylamides and aryl aldehydes using CuCl2/TBHP (tert-butyl hydroperoxide) as a catalyst and oxidant was developed.

Synthesis of Chiral C 1-Symmetric N-Heterocyclic Carbene Ligands: Application toward Copper-Catalyzed Homocoupling of 2-Naphthols

Novel chiral C 1-symmetric NHC ligands can be prepared via dialkylation of chiral imidazoline scaffolds. Asymmetry in the ligand/metal complexes results from a chiral relay effect. The C 1-symmetric nature of the NHC ligand was proposed to allow for improved reactivity versus other achiral and chiral NHC complexes. The benefit of such ligands was demonstrated in copper-catalyzed oxidative coupling reactions.

Copper-catalyzed oxidative coupling of carboxylic acids with formamides for the synthesis of α,β-unsaturated amides

A novel and efficient protocol for the synthesis of α,β-unsaturated amides has been developed using catalytic amount of Cu(OAc)2 and TBHP as an available oxidant. Oxidative coupling of various unsaturated carboxylic acids with N,N-disubstituted formamides was examined to furnish the desired products in good yields.

Effects of ligand and cosolvent on oxidative coupling polymerization of 2,6-dimethylphenol catalyzed by chelating amine-copper(II) complexes

The influence of chelating amine ligands, copper precursors, and solvent composition on copper-catalyzed oxidative coupling of 2,6-dimethylphenol was investigated. The most efficient catalytic reaction was conducted with CuCl2-di-tert-butylethylenediamine (Dt-BEDA) complex in anisole or toluene with alcohol cosolvent. Slight structural changes in the N-substituent, backbone, or coordination atom of the ligand significantly dropped catalytic activities, leading to a low polymer yield. Alcohol cosolvent was necessary to synthesize a polymer of high molecular weight \(\left( {\overline {M_n } > 10,000} \right)\) with the copper(II) catalyst in toluene. With increasing alcohol ratios, the isolated yields and \(\overline {M_n }\) values of the resulting polymers gradually decreased. However, the use of sterically bulky t-butanol produced polymers of the desired molecular weight ranges with low polydispersity indexes (PDI, <2) and without a significant drop in isolated yield. Open image in new window

Enaminone ligand-assisted homo- and cross-coupling of terminal alkynes under mild conditions

Abstract Copper-catalyzed oxidative coupling reactions of terminal alkynes have been performed at room temperature by using enaminone as effective ligand. Both symmetrical and unsymmetrical 1,3-diynes bearing various functional groups have been synthesized in moderate to excellent yields via homo- and cross-coupling reactions.