Copper‐Catalyzed Activation of Dioxygen: Oxidative Cyclization of 2‐Arylindoles

A series of unusual six‐ring‐fused heterocycles containing indole and quinoline skeletons was successfully synthesized by a copper‐catalyzed reaction from 2‐arylated indoles. Two new bonds were regioselectively formed from C H and C H coupling. ¹⁸O‐Labelled experiments revealed that the dioxygen is not only the oxidant but also the reactant.     

A Simple Copper‐Catalyzed Cascade Synthesis of 2‐Amino‐1H‐indole‐3‐carboxylate Derivatives

We have developed a simple and efficient copper‐catalyzed method for the synthesis of 2‐amino‐1H‐indole‐3‐carboxylate derivatives via cascade reactions of substituted N‐(2‐halophenyl)‐2,2,2‐trifluoroacetamide with alkyl 2‐cyanoacetate or malononitrile under mild conditions, and the method is of wide practical application.     

Copper‐Catalyzed Domino Synthesis of Isoquinolino[2,3‐a]quinazolinones

A copper‐catalyzed domino method for synthesis of isoquinolino[2,3‐a]quinazolinones has been developed using readily available, substituted methyl 2‐(2‐haloobenzamido)benzoates and nitriles as the starting materials. The domino process comprises an Ullmann‐type C‐arylation, intramolecular addition of NH with CN, and nucleophilic attack of amino to ester group. The inexpensive, convenient and efficient copper‐catalyzed method should provide a new and useful strategy for constructing nitrogen heterocycles.     

Copper(I)‐Catalyzed Synthesis of Chlorinated Tetrahydropyridazin‐3‐ones and 1,2‐Diazepan‐3‐ones from N‐Allyl‐N′‐trichloroacetylhydrazines

The synthesis of chlorinated tetrahydropyridazin‐3‐ones and 1,2‐diazepan‐3‐ones has been developed. The present paper describes the application of Cu(I)‐catalyzed ATRC for the synthesis of heterocyclic molecules containing two heteroatoms (i.e., nitrogen) in the ring for the first time. An easy separation of the individual compounds from the product mixture could be achieved by considering their solubility/insolubility in n‐hexane. The presence of three chlorine atoms provides possibilities for further derivatization.

     

Enantioselective Copper‐Catalyzed Intramolecular N−H Bond Insertion: Synthesis of Chiral 2‐Carboxytetrahydroquinolines

The first highly enantioselective intramolecular N−H bond insertion was realized by using copper catalysts modified with chiral spirobisoxazoline ligands, which provides a novel strategy for the synthesis of chiral 2‐carboxytetrahydroquinolines. This reaction features fast reaction rate, high yield, high enantioselectivity, and mild reaction conditions.

     

Synthesis of 4‐Aryl‐2‐Quinolones via Copper‐Catalyzed Hydroarylation of (o‐Aminophenyl)propiolates with Arylboronates

4‐Aryl‐2(1H)‐quinolones were efficiently synthesized via copper‐catalyzed hydroarylation of (o‐aminophenyl)propiolates with arylboronic acid neopentyl glycol esters. The substrate propiolates were prepared from the corresponding silylalkynes with carbon dioxide by Kondo’s carboxylation method using N,N‐dimethylformamide as a solvent. Hydroarylation was performed in the presence of 3 mol% copper(II) acetate in methanol at 28 °C for 12 h and subsequent deprotection using trifluoromethanesulfonic acid (3.0 equiv.) at 65 °C for 2 h in the same pot to afford the desired 4‐aryl‐2(1H)‐quinolones in 39–89% yields.

     

Retraction: Copper‐Catalyzed Cascade Reaction for Practical and Efficient Synthesis of Alkyl 2H‐Isoindole‐1‐carboxylates

The above article in Advanced Synthesis & Catalysis, published online on December 8, 2011, in Wiley Online Library (onlinelibrary.wiley.com), and in print Volume 353, Issue 18, 2011, pages 3330–3334 (DOI: 10.1002/adsc.201100451 ), has been retracted by agreement between the authors, the journal Editor, Joe P. Richmond, and Wiley‐VCH Verlag GmbH & Co. KGaA. The retraction has been agreed to for the following reasons. As determined by X‐ray analysis carried out by Jérôme Thibonnet and co‐workers, Université François Rabelais, Tours, the products reported are not isoindoles, but rather the corresponding indoles. The reaction mechanism reported is therefore also incorrect.     

Copper‐Catalyzed Three‐Component Synthesis of 2‐Iminodihydrocoumarins and 2‐Iminocoumarins

An efficient synthesis of N‐sulfonyl‐substituted 2‐imino‐3,4‐dihydrocoumarins and 2‐iminocoumarins via a copper‐catalyzed multicomponent reaction of sulfonyl azides with terminal alkynes and β‐(ortho‐hydroxyphenyl)‐α,β‐unsaturated ketones or ortho‐hydroxyphenylpropiolates has been developed. The cascade process involves trapping the keteimine by a nucleophilic addition and an intramolecular Michael addition. This methodology could well be extended to the concise synthesis of the polysubstituted piperidine scaffold.     

Retracted: Copper‐Catalyzed Cascade Reaction for Practical and Efficient Synthesis of Alkyl 2H‐Isoindole‐1‐carboxylates

The copper‐catalyzed cascade reaction comprising the condensation/α‐arylation between 2‐halobenzaldehydes and α‐amino acid esters provides a straightforward methodology for the efficient synthesis of alkyl 2H‐isoindole‐1‐carboxylates.     

Platinum‐Catalyzed Divergent Reactivity of α‐Hydroxyallenes: Synthesis of Dihydrofurans and α,β‐Unsaturated Ketones

α‐Allenols were catalytically transformed into dihydrofurans in the presence of platinum dichloride. Notably, using platinum dichloride along with silver triflate as the catalytic system, α,β‐unsaturated ketones were obtained. Therefore, the role of the silver salt may not just consist in the activation of the platinum precatalyst.

     

Cupric Halide‐Mediated Intramolecular Halocyclization of N‐Electron‐Withdrawing Group‐Substituted 2‐Alkynylanilines for the Synthesis of 3‐Haloindoles

A convenient and efficient method for the synthesis of 3‐haloindoles has been developed. Both 3‐chloro‐ and 3‐bromoindole derivatives can be obtained in high yields by the reaction of N‐electron‐withdrawing group‐substituted 2‐alkynylanilines with cupric halide in dimethyl sulfoxide (DMSO) within a short period of time. Investigation of the reaction mechanism reveals that two equivalents of cupric halide are necessary.     

Highly Practical “Ligand‐Free‐Like” Copper‐Catalyzed N‐Arylation of Azoles in Lower Nitrile Solvents

In lower nitrile solvents, the N‐arylation of azoles with aryl halides was achieved efficiently in the presence of copper powder without any additional ligands. Thus, the first nitrile type of monodentate ligand‐mediated, “ligand‐free‐like” copper‐catalyzed N‐arylation procedure was established.     

Copper‐Catalyzed Chloroamination of Alkynes: Highly Regio‐ and Stereoselective Synthesis of (E)‐β‐Chloro‐Enesulfonamides

An efficient copper catalysis system for the chloroamination of alkynes with chlorosulfonamide at room temperature is described, providing a highly regio‐ and stereoselective procedure for the synthesis of (E)‐β‐chloro‐enesulfonamides in moderate to good yields.     

Copper‐Catalyzed Monoborylation of Silylalkynes; Regio‐ and Stereoselective Synthesis of (Z)‐β‐(Borylvinyl)silanes

The selective copper‐catalyzed borylation of silylalkynes in the presence of a diboron reagent and methanol produced a variety of (Z)‐β‐(borylvinyl)silanes. The appropriate use of a selective ligand for copper allows the chemo‐, regio‐, and stereoselective monoborylation of silylalkynes. The β‐regioselectivity of an N‐heterocyclic carbene (NHC)‐copper catalyst was investigated by DFT calculations.

     

Palladium/Copper‐Catalyzed Di‐α‐arylation of Acetic Acid Esters

A bimetallic palladium/copper catalyst system was found to effectively promote the diarylation of alkyl acetates with aryl halides under unprecedentedly mild conditions. The phenanthroline‐copper‐phosphine catalyst stabilizes the enolate intermediate to the extent that the deprotonation of esters can be achieved even with the mild base potassium phosphate. The palladium tri‐tert‐butylphosphine co‐catalyst mediates the coupling of the resulting copper enolate with a wide variety of aryl halides with selective formation of the corresponding diarylacetic acid esters.     

The Copper‐Catalyzed Oxidative N‐Acylation of Sulfoximines

An oxidative cross‐coupling reaction between aldehydes and sulfoximines involving dual C H/N H functionalization has been developed. This reaction process is facilitated by a simple copper catalyst (1 mol% loading) and tert‐butyl hydroperoxide (TBHP) as the oxidant and proceeds under mild reaction conditions to afford a series of valuable N‐acylated sulfoximine derivatives in excellent yields.     

Synthesis of Chiral N‐Sulfonyl and N‐Phosphinoyl α‐Halo Aldimine Precursors

α‐Halogenated aldimines have emerged as an important class of synthetic intermediates. The stability and reactivity of α‐halo aldimines can vary greatly depending on the nitrogen protecting group. A general synthesis of stable, chiral α‐halo‐N‐sulfonyl and N‐phosphinoyl aldimine precursors is presented (42–96% yield). The corresponding α‐halo aldimines can be isolated upon treatment with a mild base. Enantioenriched α‐chloro aldehydes can be employed to afford aldimine precursors with no erosion of optical purity. Both the enantioenriched aldimine precursor and the isolated aldimine can react with an alkynyllithium nucleophile to give trans‐β‐chloroamine products with excellent dr. Ring closure affords the enantioenriched trans‐aziridine, demonstrating the potential for this approach in complex molecule synthesis.