Efficient and Versatile Synthesis of Indoles from Enamines and Imines by Cross-Dehydrogenative Coupling

Transition-metal-free, visible-light-mediated cyclization of o-azidoarylalkynes with aryl diazonium salts

A visible-light promoted transformation of o-azidoarylalkynes and aryl diazonium salts for the synthesis of unsymmetrical 2,3-diaryl-substituted indoles under transition-metal-free conditions was described.

Transition-metal-free, visible-light induced cyclization of arylsulfonyl chlorides with o-azidoarylalkynes: a regiospecific route to unsymmetrical 2,3-disubstituted indoles

A visible-light-catalyzed synthesis of unsymmetrical 2,3-diaryl-substituted indoles from arylsulfonyl chlorides and o-azidoarylalkynes at room temperature has been discovered.

Introducing tetramethylurea as a new methylene precursor: a microwave-assisted RuCl3-catalyzed cross dehydrogenative coupling approach to bis(indolyl)methanes

The microwave-assisted synthesis of symmetrical/unsymmetrical bis(indolyl)methanes using tetramethylurea as a methylene source.

Palladium-catalyzed oxidative arylacetoxylation of alkenes: synthesis of indole and indoline derivatives

A method for the oxidative arylacetoxylation of alkenes has been developed to synthesize indole and indoline derivatives from readily accessible substrates.

Electrocatalytic intramolecular oxidative annulation of N-aryl enamines into substituted indoles mediated by iodides

An electrocatalytic reaction protocol is developed for achieving intramolecular dehydrogenative annulation ofN-aryl enamines.

Catalytic Synthesis of Substituted Indoles and Quinolines from the Dehydrative C-H Coupling of Arylamines with 1,2- and 1,3-Diols

The cationic ruthenium-hydride complex catalyzes dehydrative C-H coupling reaction of arylamines with 1,2-diols to form the indole products. The analogous coupling of arylamines with 1,3-diols afforded the substituted quinolines. The catalytic method directly forms these coupling products in a highly regioselective manner without generating any toxic byproducts.

Dehydrogenative [2 + 2 + 1] Heteroannulation Using a Methyl Group as a One-Carbon Unit: Access to Pyrazolo[3,4-c]quinolines

A practical and straightforward access to pyrazolo[3,4-c]quinolines by molecular sieve mediated dehydrogenative [2 + 2 + 1] heteroannulation of N-(o-alkenylaryl)imines with aryldiazonium salts is described using a sp(3)-hybrid carbon atom as a one-carbon unit. The reaction enables the formation of three new chemical bonds, a C-C bond and two C-N bonds, in a single reaction and features simple operation and excellent functional group tolerance.

Synthesis of Organofluoro Compounds Using Methyl Perfluoroalk-2-ynoates as Building Blocks

This review provides an overview of several synthetic applications of methyl perfluoroalk-2-ynoates, leading to convenient preparation of many perfluoroalkylated compounds. The use of these important substrates in the synthesis of various five-, six-, and seven-membered heterocycles, cyclopentadienes, and biphenyls is described, alongside a discussion of the mechanistic aspects of these reactions.

Intramolecular cross dehydrogenative coupling of 4-substituted coumarins: rapid and efficient access to coumestans and indole[3,2-c]coumarins

A palladium-catalyzed highly efficient and atom-economical intramolecular cross dehydrogenative coupling (CDC) reaction to access fused polyheterocycles containing a coumarin nucleus has been developed.

Synthesis of 2-oxophosphorindolines via the copper-catalyzed intramolecular aromatic C–H insertion of diazophosphonamidates

2-Ethoxy-2-oxophosphorindolines, benzo-γ-phospholactams, were synthesized efficiently with up to 97% yield through the copper-catalyzed intramolecular aromatic C–H insertion of diazophosphonamidates.

Divergent synthesis of indoles, oxindoles, isocoumarins and isoquinolinones by general Pd-catalyzed retro-aldol/α-arylation

Divergent synthesis of indoles, oxindoles, isocoumarins and isoquinolinones is achieved by a general Pd-catalyzed retro-aldol reaction of β-hydroxy ketones/esters with aryl halides bearing an ortho-nitro, -ester or -nitrile group. DFT insights have been presented to rationalize the experimental observations and the chemoselectivity.

Brønsted acid cocatalysis in photocatalytic intramolecular coupling of tertiary amines: efficient synthesis of 2-arylindols

We report herein a highly efficient intramolecular coupling reaction of tertiary amines and ketones (α,β-unsaturated ketones) by using a Brønsted acid as a cocatalyst, affording 2-arylindols in good to excellent yields (up to 92%) under visible light irradiation at room temperature.

Divergent reactivity in palladium-catalyzed annulation with diarylamines and α,β-unsaturated acids: direct access to substituted 2-quinolinones and indoles

A palladium-catalyzed CH activation strategy has been successfully employed for exclusive synthesis of a variety of 3-substituted indoles. A [3+3] annulation for synthesizing substituted 2-quinolinones was recently developed by reaction of α,β-unsaturated carboxylic acids with diarylamines under acidic conditions. In the present work, an analogous [3+2] annulation is achieved from the same set of starting materials under basic conditions to generate 1,3-disubstituted indoles exclusively. Mechanistic studies revealed an ortho-palladation-π-coordination-β-migratory insertion-β-hydride elimination reaction sequence to be operative under the reaction conditions.

Synthesis of 3-Iminoindol-2-amines and Cyclic Enaminones via Palladium-Catalyzed Isocyanide Insertion-Cyclization

A palladium-catalyzed isocyanide insertion-cyclization using low-cost and readily accessible 2-haloanilines, 2-iodophenylethanones, and isocyanides for efficient synthesis of 3-iminoindol-2-amine and cyclic enaminone derivatives has been developed. The method features low-cost and readily accessible starting materials, reliable scalability, and bond-forming efficiency as well as simple one-pot operation, which makes this strategy highly attractive. A reasonable mechanism for forming 3-iminoindol-2-amine involved double isocyanide insertion/cyclization process is proposed.

Palladium-catalyzed intermolecular oxidative cyclization of N-aryl enamines with isocyanides through double sp2 C–H bonds cleavage: facile synthesis of 4-aminoquinoline derivatives

An efficient method for the synthesis of 4-aminoquinolines via palladium-catalyzed intermolecular oxidative cyclization of N-aryl enamines and isocyanides through double sp² C–H bonds cleavage has been developed.

Rh(iii)-catalyzed 7-azaindole synthesis via C–H activation/annulative coupling of aminopyridines with alkynes

An efficient Rh(iii)-catalyzed 7-azaindole synthesis was developed via C–H activation/annulative coupling of aminopyridines with alkynes.

NIS-mediated intramolecular oxidative α-functionalization of tertiary amines: transition metal-free synthesis of 1,2-dihydro-(4H)-3,1-benzoxazin-4-one derivatives

A novel method for direct α-functionalization of tertiary amines via NIS-mediated oxidative C–O bond formation, where NIS serves as both an oxidant and an iodination reagent, has been developed.

Metal-free nitrative cyclization of N-aryl imines with tert-butyl nitrite: dehydrogenative access to 3-nitroindoles

A novel metal-free oxidative C–H functionalization and nitrative cyclization access to 3-nitroindoles from N-aryl imines is described.