Copper-Catalyzed <i>N</i>- and <i>O</i>‑Alkylation of Amines and Phenols using Alkylborane Reagents

By the reaction of amines with alkylborane reagents in the presence of a catalytic amount of copper(II) acetate Cu(OAc)₂ and di-<i>tert</i>-butyl peroxide, a cross-coupling reaction proceeded and alkylated amines were obtained in good to excellent yields. Phenols are also applicable for this reaction, and the corresponding alkyl aryl ethers were produced

Rhenium-Catalyzed Regioselective Alkylation of Phenols

Rhenium-Catalyzed Regioselective Alkylation of Phenol

Copper-Catalyzed Intramolecular N–S Bond Formation by Oxidative Dehydrogenative Cyclization

Copper-catalyzed synthesis of benzo­[<i>d</i>]­isothiazol-3­(2<i>H</i>)-ones and <i>N</i>-acyl-benzothiazetidine by intramolecular dehydrogenative cyclization is described. In this reaction, a new nitrogen–sulfur (N–S) bond is formed by N–H/S–H coupling. The present reaction has high functional group tolerance and gives products in gram scale. This method promotes double cyclization, allowing for synthesis of a drug intermediate

Sequential Ruthenium-Catalyzed Hydroamination and Rhenium-Catalyzed C−H Bond Activation Leading to Indene Derivatives

Formal [3+2] annulation of arylacetylenes and α,β-unsaturated carbonyl compounds is achieved in a one-pot reaction by successive treatment of the acetylenes with aniline and a catalytic amount of Ru3(CO)12 and NH4PF6 and C−H bond activation catalyzed by [ReBr(CO)3(thf)]2. The result suggests that the second rhenium-catalyzed indene formation is not disturbed by the first catalyst system

Copper-Mediated Direct C(sp³)–H and C(sp²)–H Acetoxylation

A copper-mediated terminal position-selective C­(sp3)–H acetoxylation using a bidentate directing group and AgOAc as an oxidant was achieved. This reaction has high functional group tolerance and is not affected by steric hindrance. The reaction proceeds in excellent yield, even in gram scale, and the directing group can be removed after the reaction. Aromatic C­(sp2)–H acetoxylation also proceeded under similar reaction conditions

Rhenium-Catalyzed Formation of Indene Frameworks via C−H Bond Activation: [3+2] Annulation of Aromatic Aldimines and Acetylenes

A rhenium complex, [ReBr(CO)3(thf)]2, catalyzes the reaction of an aromatic aldimine with an acetylene to give an indene derivative in a quantitative yield. The reaction proceeds via C−H bond activation, insertion of the acetylene, intramolecular nucleophilic cyclization, and reductive elimination. In contrast to ruthenium and rhodium catalysts, which are usually employed in this type of reaction, the rhenium catalyst promotes the intramolecular nucleophilic cyclization of the alkenylmetal species generated by insertion of the acetylene

Rhenium-Catalyzed Insertion of Terminal Acetylenes into a C−H Bond of Active Methylene Compounds

A rhenium complex, [ReBr(CO)3(thf)]2, catalyzed the intermolecular reactions of 1,3-dicarbonyl compounds with terminal acetylenes and gave the corresponding alkenyl derivatives in excellent yields. These reactions could apply to an intramolecular version and gave the corresponding cyclic compounds quantitatively

Decatungstate-Catalyzed C(sp³)–H Alkylation of a Val Residue Proximal to the N‑Terminus Controlled by an Electrostatic Interaction

The decatungstate photocatalyst [W10O32]4– efficiently promoted the C­(sp3)–H alkylation of the trifluoroacetic acid salt of valine methyl ester (H-Val-OMe·TFA) with electron-deficient alkenes under UV irradiation. The electrostatic interaction between the cationic ammonium group (+NH3) of the main chain and anionic [W10O32]4– played an important role in this reaction. The influence of various protected amino acids in the C­(sp3)–H alkylation was investigated as the model reaction for the alkylation of Val-containing peptides. The introduction of an alkyne moiety into Val through this alkylation was successful, and successive copper-catalyzed azide–alkyne cycloaddition (CuAAC) was demonstrated. The C­(sp3)–H bond of a Val residue located at the second from the N-terminus was also successfully converted. C­(sp3)–H alkylation of oligopeptides containing two Val residues selectively proceeded proximally to the N-terminus

Rhenium-Catalyzed Regio- and Stereoselective Synthesis of γ‑Thio-α,β-unsaturated Ketones via Insertion of Terminal Alkynes into the C–S Bond

The reaction of α-thioketones and alkynes in the presence of a rhenium catalyst, [HRe(CO)₄]_<i>n</i>, gave γ-thio-α,β-unsaturated ketones in excellent yields. The alkynes were inserted into the carbon–sulfur bond of the α-thioketones, and isomerization of a double bond provided the products with high regio- and stereoselectivities. This reaction also proceeded in an intramolecular fashion