Generation of N-Heterocycles via Tandem Reactions ofN ′-(2-Alkynylbenzylidene)hydrazides

Silver(I)-Promoted [3 + 3]-Cycloaddition of 2-(2-Enynyl)quinolines with N'-(2-Alkynylbenzylidene)hydrazides

An effective and straightforward Ag(I)-mediated annulation of 2-(2-enynyl)quinolines and N'-(2-alkynylbenzylidene)hydrazides was developed, forging various synthetically challenging 17bH-isoquinolino[2'',1'':1',6']pyridazino[4',5':3,4]pyrrolo[1,2-a]quinolines, including different nitrogen-containing fused rings, in moderate to excellent yields. This one-pot cycloaddition strategy features exclusive regioselectivity, high atom economy, and broad substrate scope under mild conditions. The practicality and reliability of this cycloaddition reaction was demonstrated by a successful scale-up synthesis.

Regio- and Diastereoselective Radical Dimerization Reactions for the Construction of Benzo[f]isoindole Dimers

This study presents a novel approach for synthesizing benzo[f]isoindole dimers, which involves cascade cyclization and oxidative radical dimerization. Our method allows for the formation of up to five carbon-carbon bonds in a single reaction, exhibiting remarkable diastereoselectivity and regioselectivity. The mechanism and regioselectivity were investigated through a combination of experiments and calculations.

Sequential Ag(I) Salt and Chiral N-Heterocyclic Carbene Catalysis Enables Enantioselective and Diastereoselective Construction of Complex Heterocyclic Molecules and the Switch of Stereoselectivity

Organic reactions under cascade catalysis provide a powerful strategy to construct molecules of complexed structures. Reported herein is the sequential silver(I) salt and chiral N-heterocyclic carbene (NHC) catalyzed enantioselective and diastereoselective synthesis of a diversity of unprecedented fused heterocyclic compounds from the reactions of readily available N'-((2-alkynyl-3-pyridinyl)methylene)hydrazides with 2-aroylvinylcinnamaldehydes. Both reaction pathways and stereoselectivity were steered conveniently and efficiently by the employment of different NHCs and bases, enabling the selective preparation of pentacyclic ring-fused 1,6-naphthyridine derivatives and 1,6-naphthyridine-substituted tricyclic products in moderated to good yields with high enantioselectivity and diastereoselectivity. Mechanisms accounting for the selective transformations, especially the effect of base and chiral NHC catalyst on the reaction course and stereochemistry of products, were also discussed.

Synthesis of Trifluoromethyl- and Ester Group-Substituted α-Carbolines via Iron-Catalyzed Tandem Cyclization Reaction

An efficient approach to prepare trifluoromethyl-α-carbolines and ester group-substituted α-carbolines via the tandem cyclization reaction of 2-(2-aminophenyl)acetonitriles and trifluoromethyl 1,3-diones or β,γ-unsaturated α-ketoesters was reported. The transformation proceeded smoothly in the presence of catalytic environmental-benign iron salts, which are used to prepare the desired products in moderate to good yields.

Construction of enantiopure imine bridged benzo[c]azepinones by a silver(i) and chiral N-heterocyclic carbene multicatalytic reaction sequence of N′-(2-alkynylbenzylidene)hydrazides and cyclopropanecarbaldehydes

A novel and efficient method for the synthesis of enantiopure bridged benzo[c]azepinone compounds has been developed by metal/N-heterocyclic carbene multicatalysis.

Copper-catalyzed synthesis of pyrazolo[5,1-a]isoquinoline derivatives from 2-gem-dipyrazolylvinylbromobenzenes

An efficient copper-catalyzed synthesis of pyrazolo[5,1-a]isoquinolines from 2-gem-dipyrazolylvinylbromobenzenes under mild conditions has been developed.

ortho-Amide-directed 2,4-dibromohydration of conjugated enynes

A NBS-mediated and ortho-amide-directed 2,4-dibromohydration of enynes is described in this paper.

Regioselective 5-exo-dig oxy-cyclization of 2-alkynylbenzamide for the synthesis of isobenzofuran-1-imines and isobenzofuran

A TBAB-mediated regioselective radical cyclization of 2-alkynylbenzamide is described herein for the synthesis of isobenzofuran-1-imines. The reactions proceeded smoothly under mild conditions.

C(sp2)–H functionalization of aldehyde-derived hydrazones via a radical process

This review is focused on the recent advances in the C(sp²)–H functionalization of aldehyde-derived hydrazones via a radical process. Diverse substituted hydrazones including N-heterocycles are afforded under mild conditions with excellent selectivities. In general, an aminyl radical as the key intermediate is involved during the reaction process.

Generation of benzosultams via a radical process with the insertion of sulfur dioxide

A three-component reaction of 2-ethynylbenzenesulfonamides, DABCO-bis(sulfur dioxide), and aryldiazonium tetrafluoroborates affords sulfonated benzosultams in moderate to good yields. This reaction proceeds through a tandem radical process. DABCO acts as a carrier for single electron transfer, as well as a base to promote the C–N bond formation.

Synthesis of polycyclic sultams via a palladium-catalyzed reaction of 1-bromo-2-(cyclopropylidenemethyl)benzenes with 2-alkynylbenzenesulfonamides

Polycyclic sultams are efficiently synthesized through a palladium-catalyzed tandem reaction of 1-bromo-2-(cyclopropylidenemethyl)benzenes with 2-alkynylbenzenesulfonamides via double carbometallation.

Synthesis of benzil-o-carboxylate derivatives and isocoumarins through neighboring ester-participating bromocyclizations of o-alkynylbenzoates

Neighboring ester-participating bromocyclizations of o-alkynylbenzoates are developed for the switchable synthesis of benzil-o-carboxylate derivatives and isocoumarins.

A palladium-catalyzed tandem reaction of 2-alkynylbenzenesulfonamides with 2-(2-bromoarylidene)cyclobutanones

The core of benzo[f][1,2]thiazonin-5(4H)-one 3,3-dioxide is efficiently assembled through a palladium-catalyzed tandem reaction of 2-alkynylbenzenesulfonamides with 2-(2-bromobenzylidene)cyclobutanones via double carbometallation. A range of polycycles with a nine-membered sultam ring are generated in moderate to good yields.

A copper(ii)-catalyzed three-component reaction of aryldiazonium tetrafluoroborates, sulfur dioxide, with alkenes

A three-component reaction of aryldiazonium tetrafluoroborates, sulfur dioxide, with alkenes catalyzed by copper(ii) bromide is developed, which provides an efficient route to (E)-alkenyl sulfones or allylic sulfones via the insertion of sulfur dioxide.

Base-controlled [3+3] cycloaddition of isoquinoline N-oxides with azaoxyallyl cations

A base-controlled [3+3] cycloaddition reaction of isoquinoline N-oxides with azaoxyallyl cations is developed, leading to 1,11b-dihydro-[1,2,4]oxadiazino[3,2-a]isoquinolin-2(3H)-ones and 2-(isoquinolin-1-yloxy)acetamides, respectively. This transformation proceeds through an azaoxyallyl cation generated in situ from α-bromohydroxamate.

Synthesis of trifluoromethylated 3,4-dihydroquinolin-2(1H)-ones via a photo-induced radical cyclization of benzene-tethered 1,7-enynes with Togni reagent

A photoinduced radical cyclization of benzene-tethered 1,7-enynes with Togni reagent in the presence of sodium iodide is developed. This transformation works well without any metals or photo-redox catalysts at room temperature.

Generation of benzosultams via trifluoromethylation of 2-ethynylbenzenesulfonamide under visible light

Under visible light irradiation, 2-ethynylbenzenesulfonamides react with Togni's reagent in the presence of a photocatalyst leading to 3-(2,2,2-trifluoroethylidene)-2,3-dihydrobenzo[d]isothiazole 1,1-dioxides in good yields. This transformation proceeds efficiently at room temperature through a photo-initiated trifluoromethylation.

Generation of (2-oxoindolin-3-yl)methanesulfonohydrazides via a photo-induced reaction of N-(2-iodoaryl)acrylamide, DABSO, and hydrazine

A photo-induced catalyst-free three-component reaction of N-(2-iodoaryl)acrylamide, sulfur dioxide, and hydrazine is reported. Under ultraviolet irradiation, diverse (2-oxoindolin-3-yl)methanesulfonohydrazides are generated in moderate to good yields.

Synthesis of pyrazolo[5,1-a]isoquinolines via a silver(i)-catalyzed reaction of (1-arylethylidene)hydrazides with N′-(2-alkynylbenzylidene)hydrazides

A silver(i)-catalyzed reaction of (1-arylethylidene)hydrazides with N′-(2-alkynylbenzylidene)hydrazides via [3 + 2] cycloaddition and intramolecular rearrangement is reported, which proceeds through azo-alkene and isoquinolinium-2-yl amide intermediates.