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Backgroup: The versatile 2-alkynylbenzamde has been reported to produce many privileged skeletons, like isoquinolin-1-ones, isocoumarin-1-imines, isoindolin-1-ones, and isobenzofuran-1-imines. Recently, we reported the projected transformation using copper salt (CuCl2) as a catalyst under O2 atmosphere. To expand the scope of reaction we used another inexpensive metal salt MnO2 as catalyst Methods: The paper aims at exploring a manganese-catalyzed reaction of 2-alkynylbenzamide under O2 balloon for the synthesis of 3-hydroxylisoquinolin-1,4-dione. Results: Results on reaction scope shows the 10 mol% MnO2 in O2 atmosphere and DCE solvent catalyzed the cyclization of 2-alkynylbenzamide to produce 3-hydroxylisoquinolin-1,4-diones in 40-68% isolated yields. The reaction proceeds through a regioselective N-center radical 6-endo-dig aza-cyclization pathway. Conclusion: We have developed a manganese-catalyzed cyclization of 2-alkynlbenzamide for the synthesis of 3-hydroxylisoquinolin-1,4-diones under O2 balloon. It is believed that the N-center radical-based 6-endo dig aza-cyclization proceeded in a regioselective manner.

In this work, the use of

A reductive coupling reaction of sodium sulfinates for the synthesis of symmetrical/unsymmetrical thiosulfonates is developed. The reaction takes place in the presence of acetyl chloride and Hantzsch ester under mild conditions and exhibits broad functional group tolerance. Mechanistic studies suggest that a radical process is involved.

A blue LED-promoted dearomative oxo-spirocyclization of N-aryl-N-(2-hydroxyethyl)propiolamides is developed. The reaction works well to provide a series of selenium-containing benzo[b]pyrrolo[2,1-c][1,4]oxazine-3,9-diones with high efficiency and good tolerance for functional groups. Besides, diselenium-containing benzo[b]pyrrolo[2,1-c][1,4]oxazine-3,9-diones can also be efficiently synthesized in the presence of Oxone. In this process, it is believed that a selenium radical-triggered ipso-cyclization and oxo-Michael addition are involved. Further applications using the prepared products in bioactivity assay is currently underway.

This review summarizes recent advances in the use of isocyanide as “C1N1” synthons in cyclization.

In this work, iron/photoredox dual-catalyzed acyl nitrene formation and the use of acyl nitrene in constructing various C–O bonds are reported for the synthesis of phthalides.

Recent advances in nitrene chemistry from acyclic precursors are reviewed in this paper. Early developments in nitrene chemistry predominantly focused on exploiting new nitrene precursors and inventing new types of nitrene-based transformations. Organic azides, iminoiodinanes (even in situ generated iminoiodinanes), amines, and amide N–O compounds have all been reported as efficient acyclic nitrene precursors. Nitrene-based transformations mainly include C–H amination/amidation, aziridination, addition to unsaturated bonds, sulfimidation, etc. In many cases, asymmetric versions of C–H amination/amidation, aziridination and sulfimidation have been demonstrated. In this review, a particular emphasis is placed on reactions of nitrene with unsaturated bonds and reactions using amide N–O compounds as nitrene precursors. It can be seen that the reactivity of nitrene species can be controlled by the metal centre, ligand, type of nitrene precursor, and reaction system.

A palladium-catalyzed [4 + 1] cycloaddition of prop-2-yn-1-ones with double isocyanides is developed herein. The transformation worked well to produce a series of 2-amino-4-cyanofurans with high efficiency and a broad reaction scope. Based on mechanism studies, it is believed that the palladium-catalyzed [4 + 1] imidoylative cycloaddition of prop-2-yn-1-ones was concerted. Treated with aryl amine and H2O, the [4 + 1] cycloaddition of prop-2-yn-1-ones with double isocyanides provided 2-amino-4-amidylpyrroles efficiently.

A facile procedure is reported for the synthesis of various 2-bromo-1-phenyl-5,6-dihydro-3H,7aH-benzo[b]pyrrolo[2,1-c][1,4]oxazin-3-ones via a radical bromination-induced ipso cyclization–ortho cyclization sequence of N-arylpropiolamides in the presence of TBAB and oxone. The radical cyclization sequence involves a radical bromo α-addition into the alkyne, ipso-cyclization, and ortho-trapping of the spirocyclic intermediate.

In this work, by using N-methoxybenzamides as efficient acyl nitrene precursors, an iron-catalyzed acyl nitrene/alkyne metalation is reported for the synthesis of pyrrolo[2,1-a]isoindol-5-ones. In the reaction, a 5-exo-dig acyl nitrene/alkyne metalation is specifically observed; a counter anion-aided acyl nitrene/alkyne metalation accounts for the formation of pyrrolo[2,1-a]isoindol-5-ones. Moreover, pyrrolo[2,1-a]isoindol-5-ones possess good fluorescence properties exhibiting a long Stokes shift (>100 nm), and have been employed as small molecular probes for the detection of Hg2+, hydrazine, and cysteine.

In recent years, one of the main research interests of our group has been the construction of 6/5 π-systems through the regioselective conversion of parallel alkynes in naphthalene with the aim of exploiting potential fluorescent materials. Herein, the copper-catalyzed synthesis of polysubstituted (Z)-2H-naphtho[1,8-bc]thiophenes from 8-halo-1-ethynylnaphthalenes using potassium ethylxanthate as the sulfur source is reported. In this protocol, a series of thiophene-fused 6/5 π-system compounds was synthesized via copper-catalyzed Ullmann-type C(aryl)–S bond formation and the α-addition of an alkyne bond with high selectivity and in high yields. The synthesized polysubstituted (Z)-2H-naphtho[1,8-bc]thiophenes exhibited solid emission, which made them potential candidates for use in optoelectronic conjugated materials. By using DMSO/D2O (3 : 1) as the reaction solvent, the deuterated products could be obtained in good yields under standard conditions.

A copper-catalyzed radical cascade dehydrogenative cyclization of N-tosyl-8-ethynyl-1-naphthylamines under air is described herein for the synthesis of thioazafluoranthenes. The reaction proceeds s...

In this work, a palladium-catalyzed [2 + 2 + 1] cyclization of internal alkynes with double isocyanides is described. This facile procedure is efficient for synthesizing various pyrrolo[3,2-c]quinolin-2-amines. The reaction worked well with a broad reaction scope. In the process, it is believed that sequential double isocyanide insertion, 6-exo-dig cyclization of alkyne, and addition of an imino group are involved.

A facile synthesis of benzo[3,4]indolo[1,2-b]isoquinolin-8-ones is described. Under copper catalysis, the reaction proceeds with a high efficiency and a broad reaction scope. A deuteration experiment shows that the KIE value is 2.85. From the results on mechanism studies, copper-catalyzed C-H activation, intramolecular cis-addition of alkynes, and reductive elimination are involved. Moreover, this skeleton is indeed a new fluorophore, and its photophysical properties are also investigated.

Lithium–sulfur batteries are attracting significant attention due to their high specific capacity, reaching 1672 mAh g–1, but their practical applications are hindered by the inherent insulation of...

In this work, a palladium-catalyzed cyclization of alkynylimines and double isocyanides is described. This facile procedure is efficient for synthesizing various 4-amidyl-2-aminopyrroles. Mechanism investigation indicates that a four-membered ring-fused pyrrole species is a key intermediate and the reaction involves [4 + 1] cycloaddition, protonation, nucleophilic addition, 1,4-addition of isocyanide, and rearomatization. Interestingly, the linear dipyrrole derivative is found to be an appropriate fluoride ion probe with a remarkable emission change, which could serve as a potential candidate for optoelectronic conjugated materials.

The microenvironment within self-assembled supramolecular coordination cages (SCCs) inaugurates a new phase of chemistry other than the conventional solid, liquid and gaseous phases. The rational design and ease of synthesis of self-assembled architectures have received tremendous attention mainly in the field of supramolecular chemistry. The structural transition from 2-D metallacycles to 3-D metallacages has led to better encapsulation and enhanced cavity effects, like restricted substrate motion, desolvation of the substrate and covalent binding of the transition state etc. Metal-mediated self-assemblies, principally known as metallo-supramolecular coordination cages (MSCCs), form a separate class of SCCs with unique chemical phenomena inside the cavities. The aesthetic structural diversity of MSCCs obtained from the rational choice of metal knots and organic linkers renders designable and programmable architectures. This review presents cavity-based applications of these MSCCs, such as molecular recognition and separation, stabilization of reactive species by encapsulation, as drug-delivery systems and as “molecular flasks” to foster reactions with unprecedented results. The objective of this review is to inspire and pave the way for researchers working in this field to design more advanced MSCCs and gain deep insight into cavity effects.

A palladium-catalyzed tandem reaction of N-(2-iodophenyl)-4-methyl-N-(propa-1,2-dien-1-yl)benzenesulfonamide with isocyanide is described to divergently produce aza-heterocyclic amides. The success of this reaction relies on a versatile synthetic intermediate, 2-(1H-indol-3-yl)ethen-1-imine, which was proposed to be generated through oxidative addition of palladium, regioselective addition of an allene group, 1,1-insertion of isocyanides, and β-H elimination.

A facile protocol for the tunable synthesis of 10-hydroxy-1-azaspiro[4.5]deca-3,6,8-trien-2-ones and benzo[b]pyrrolo[2,1-c][1,4]oxazin-3-ones is described. A tunable synthesis has been realized by the use of ZnBr2/oxone and tetra-n-butylammonium bromide (TBAB)/oxone. The reaction proceeds smoothly with high efficiency and a broad substrate scope. Mechanistic studies indicate that an N-protecting group-assisted ortho-trapping reaction is involved. In the transformation, the reaction undergoes α-addition, ipso-cyclization, and ortho-trapping of the resulting spirocyclic species.

Generation of multi-substituted pyrroles is accomplished through an unexpected iron(II)-promoted reaction of N-arylprop-2-yn-1-imines with water. This transformation proceeds smoothly with excellent chemoselectivity and regioselectivity. A stoichiometric amount of Fe(OTf)2 is necessary for the successful conversion. A Lewis acid-promoted tandem reaction pathway is proposed.

A novel halogen-radical-promoted dearomative aza-spiro­cyclization of alkynylimines for the synthesis of 3-halo-spirocyclohexadienones is described. In this process, it is believed that a radical addition, 5-exo-trig cyclization, and dearomative aza-spirocyclization are involved. Easily available starting materials, mild conditions, and a wide substrate scope make this approach potentially useful.

In this work, switchable synthesis of isoquinolin-1-one and 3-hydroxylisoquinolin-1,4-dione from 2-alkynylbenzamide is reported. The transformation works well with good yields and a broad reaction scope. The synthetic switch for providing isoquinolin-1-one and 3-hydroxylisoquinolin-1,4-dione is enabled by the use of a N2 or O2 atmosphere. Mechanism studies show that the reaction proceeds in a regioselective manner via a N-center radical 6-endo-dig aza-cyclization pathway.

The copper-catalyzed synthesis of 3-vinylisocoumarin-1-imine is reported. The transformation proceeds smoothly with good yields in THF and the regioselectivity was determined by a O-nucleo­philic 6-endo cyclization. Studies on the mechanism indicate that copper trifluoroacetate serves as a Lewis acid, and the use of vinyl-connected 2-alkynylbenzamide is important for this O-nucleophilic 6-endo cyclization.

Sulfur-containing moieties, especially thioethers (sulfides), play pivotal roles in the functionalities of many natural products, pharmaceutical compounds, and organic materials. In this review, we summarize the recent synthetic protocols of thioethers using thiolating reagents, including sulfonyl chlorides, sodium sulfinates, and sulfonyl hydrazides, as the ideal starting materials. Representative mechanisms for different types of reaction are also discussed.1 Introduction2 Synthesis of Thioethers from Sulfonyl Chlorides3 Synthesis of Thioethers from Sodium Sulfinates4 Synthesis of Thioethers from Sulfonyl Hydrazides5 Conclusion

In this work, a regioselective synthesis of isocoumarins from 2-alkynylbenzoic acid is reported. The transformations proceed smoothly with good yields in water via a metal-free radical pathway. When catalytic TBAB is employed, the reaction provides various isocoumarin derivatives according to the structures of the corresponding precursors. It is believed that TBAB serves as a phase transfer catalyst and radical initiator in the reaction. Compared to previous methodologies, the synthetic procedure reported herein provides a more environmentally benign route for the synthesis of isocoumarins.

A direct synthesis of 3-(bromomethylene)isobenzofuran-1(3H)-ones from 2-alkynylbenzoic acids is developed through a regioselective 5-exo-dig bromocyclization. The reaction proceeds smoothly with a broad substrate scope. The products can be further elaborated via a palladium-catalyze cross-coupling reaction, or can convert to other heterocycles through simple operation. Preliminary mechanistic studies reveal that this transformation undergoes a radical process.

This review is focused on the recent advances in the functionalization of allenes via radical process. Different radical partners including carbon radicals and heteroatom radicals are discussed in the reactions of allenes. Generally, the radical formed in situ would attack the allene at the central carbon leading to allyl radical intermediate. However, the formation of alkenyl radical intermediate from allene could be observed as well in some cases with high regioselectivity and stereoselectivity.

A photoredox-catalyzed sulfonylation of alkyl iodides, sulfur dioxide, and electron-deficient alkenes under mild conditions is achieved. This reaction proceeds through alkyl radicals formed in situ from alkyl iodides under visible light irradiation in the presence of a photoredox catalyst. The alkyl radical intermediates would react with sulfur dioxide leading to alkylsulfonyl radicals, which would be trapped by electron-deficient alkenes giving rise to alkyl sulfones. Various functional groups including nitro, halo, acetyl, sufonyl, and pyridinyl are all tolerated under the photoredox conditions.

Synthesis of allylic sulfones through a photoinduced three-component reaction of aryl/alkyl halides, potassium metabisulfite, and allylic bromides under ultraviolet irradiation at room temperature is developed. Diverse allylic sulfones are generated in moderate to good yields without the addition of any metals or photoredox catalysts. Different functional groups, including amino, ester, cyano, trifluoromethyl, and chloro are compatible under the conditions. Not only aryl halides but also alkyl halides are workable in the transformation. During this process, the natural abundant potassium metabisulfite is used as the source of sulfur dioxide. A plausible mechanism which involves the photoinduced C–X bond dissociation, sulfur dioxide fixation, and addition of the sulfonyl radical to allylic bromide is proposed.

In this work, a NBS-mediated 2,4-dibromohydration of enynes is described. It has been proved that ortho-acetamide participated in this 2,4-dibromohydration process. Mechanism studies show that an amide oxygen transfers into enynes to form a carbonyl of the products. One equivalent of water is incorporated into the ortho-acetamide group. The reaction proceeds smoothly with good functional tolerance and efficiency. Interestingly, the structural elaboration is also realized when NaBH4 is employed.

In this work, a selective synthetic strategy towards 1-azaspiro[4.5]deca-3,6,9-trien-8-ones from N-tosyl-N-(prop-2-yn-1-yl)aniline is developed. The transformation proceeds smoothly in a mixed solvent including acetonitrile and water when ZnBr2 and Oxone are employed. Mechanism studies show that the reaction proceeds in a regioselective manner via a radical ipso-cyclization pathway.

A TBAB-catalyzed oxidative 6-endo-dig oxy-cyclization of 2-alkynylbenzamide is described herein for the synthesis of isocoumarin-1-imines. The transformation proceeds regioselectively and provides the final products with high efficiency and a broad reaction scope. Interestingly, an array of isobenzofuran-1-imines is also achieved under standard conditions when N-phenyl 2-trimethylsilylethynylbenzamides are used as substrates. Mechanism studies show that 3-bromomethenisobenzofuran-1-imine is a pivotal intermediate, which goes through C-O bond migration and debromination to offer the final isocoumarin-1-imines.

A copper(II)-catalyzed three-component reaction of 2,3-allenoic acids, sulfur dioxide, and aryldiazonium tetrafluoroborates under mild conditions is developed, leading to 4-sulfonylated furan-2(5H)-ones in good yields. Not only sodium metabisulfite but also 1,4-diazabicyclo[2.2.2]octane-sulfur dioxide (DABCO·(SO2)2) is workable under the conditions. This transformation proceeds through a radical process initiated by the addition of arylsulfonyl radical to the C-central position of 2,3-allenoic acid. A broad substrate scope is demonstrated, and many sensitive functional groups are tolerated.

This review is focused on the recent advances in the functionalization of allenes via radical process. Different radical partners including carbon radicals and heteroatom radicals are discussed in the reactions of allenes. Generally, the radical formed in situ would attack the allene at the central carbon leading to allyl radical intermediate. However, the formation of alkenyl radical intermediate from allene could be observed as well in some cases with high regioselectivity and stereoselectivity.

In this work, by using N-methoxybenzamides as efficient acyl nitrene precursors, an iron-catalyzed formal cis-haloamidation of alkyne is reported. Without assistance of additives, the reaction worked well in the presence of 50 mol% FeCl3 or FeBr3, leading to a series of chloro/bromo-containing isoindolin-5-ones with high efficiency and wide reaction scope. In the reaction, the iron-facilitated haloamidation proceeds through a halo anion-participating concerted [3+2] cyclization to release the final products. The key intermediate ferric acyl nitrene A is generated in situ from a formal removal of MeOH.

A facile procedure is reported for the synthesis of various 2-bromo-1-phenyl-5,6-dihydro-3H,7aH-benzo[b]pyrrolo[2,1-c][1,4]oxazin-3-ones via a radical bromination-induced ipso cyclization-ortho cyclization sequence of N-arylpropiolamides in the presence of TBAB and oxone. The radical cyclization sequence involves a radical bromo α-addition into the alkyne, ipso-cyclization, and ortho-trapping of the spirocyclic intermediate.

In recent years, one of the main research interests of our group has been the construction of 6/5 π-systems through the regioselective conversion of parallel alkynes in naphthalene with the aim of exploiting potential fluorescent materials. Herein, the copper-catalyzed synthesis of polysubstituted (Z)-2H-naphtho[1,8-bc]thiophenes from 8-halo-1-ethynylnaphthalenes using potassium ethylxanthate as the sulfur source is reported. In this protocol, a series of thiophene-fused 6/5 π-system compounds was synthesized via copper-catalyzed Ullmann-type C(aryl)-S bond formation and the α-addition of an alkyne bond with high selectivity and in high yields. The synthesized polysubstituted (Z)-2H-naphtho[1,8-bc]thiophenes exhibited solid emission, which made them potential candidates for use in optoelectronic conjugated materials. By using DMSO/D2O (3 : 1) as the reaction solvent, the deuterated products could be obtained in good yields under standard conditions.

A copper-catalyzed radical cascade dehydrogenative cyclization of

A facile synthesis of benzo[3,4]indolo[1,2

In this work, a palladium-catalyzed cyclization of alkynylimines and double isocyanides is described. This facile procedure is efficient for synthesizing various 4-amidyl-2-aminopyrroles. Mechanism investigation indicates that a four-membered ring-fused pyrrole species is a key intermediate and the reaction involves [4 + 1] cycloaddition, protonation, nucleophilic addition, 1,4-addition of isocyanide, and rearomatization. Interestingly, the linear dipyrrole derivative is found to be an appropriate fluoride ion probe with a remarkable emission change, which could serve as a potential candidate for optoelectronic conjugated materials.

In this work, 1,4-dioxane-mediated hydroxylhydrative aza-cyclization of 2-alkynylbenzamide is developed for the synthesis of 3-hydroxylisoindolin-1-ones. The transformation proceeds smoothly in water with good yields and a broad reaction scope. Mechanistic studies show that regioselective brimonative 5-exo-dig aza-cyclization, bromohydration of the resulting alkene groups, and hydrolysis of dibromo compounds are involved. Compared to the traditional methodologies, the synthetic procedure reported herein represents a cleaner route toward 3-hydroxylisoindolin-1-ones.