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A one-pot two-step fashion for the synthesis of 3-trifluoromethyl-1,4-benzoxazines from CF3-imidoyl sulfoxonium ylides and 2-bromophenols via lithium-bromide-promoted O–H insertion of sulfoxonium ylides and annulation has been demonstrated.

A simple protocol for the rapid synthesis of chalcogen-containing compounds by an I2O5-promoted oxidative Csp2–H selenation and seleno/thiocyanation of activated arenes is reported here.

An efficient approach to divergently access γ-hydroxy-butenolides and γ-alkylidene-butenolides via annulation reaction of α-keto acids with simple aliphatic ketones is reported herein.

Direct synthesis of 3-acylpyrroles via acceptorless dehydrogenative coupling with the merits of high step- and atom efficiency, broad substrate scope, operational simplicity, and water and hydrogen gas as the sole by-products.

An electrochemical oxidative thio(seleno)cyanation of enamides to synthesize various (E)-β-thio(seleno)cyanated enamide compounds is reported herein.

The cascade sequential reaction of α-keto acids, 1-iodoalkynes, and alkyl halides are reported herein to synthesize tetra-substituted vinyl iodides. It represents an efficient protocol to access a diverse range of tetra-substituted vinyl iodides starting from simple materials in a one-pot fashion, featuring mild reaction conditions, ease of operation, and broad substrate scope.

A rare-earth salt Yb(OTf)3-catalyzed regioselective hydroamination of ynamides with anilines and p-toluenesulfonamide has been developed. This protocol provided facile access to a diverse range of amidines with good functional group tolerance in moderate to high yields.

Annulation reaction of α-keto acids with cyclic or acyclic aliphatic ketones is reported herein to divergently access γ-hydroxy-butenolides and γ-alkylidene-butenolides depending on the amount of BF

A direct and straightforward thiocyanation of enamides with NH4SCN under metal-free conditions has been accomplished. A variety of (E)-β-thiocyanoenamides are readily produced in a regio- and stereo-selective manner. The protocol features mild reaction conditions, good functional group tolerance and operational simplicity. The potential utility of this strategy was further demonstrated by transformation of thiocyanate into thiotetrazole-containing compounds and a Pd-catalyzed cross-coupling reaction to afford six- or seven-membered sulfur-containing heterocycles. Mechanistic insights into the reaction indicate that the reaction may proceed via a radical mechanism.

The electrochemical sulfonylation of enamides with sodium sulfinates was developed in an undivided cell in constant current mode, leading to the formation of β-amidovinyl sulfones in moderate to good yields. The catalyst-, electrolyte- and oxidant-free protocol features good functional group tolerance and employs electric current as a green oxidant. Mechanistic insights into the reaction indicate that the reaction may proceed via a radical mechanism.

The first general method for the synthesis of α-alkyl ynones was developed based on the strategy of electrophilic activation of amides. Its distinctive advantages are attributed to the use of air-stable "bare" 1-copper(I) alkyne as a mild nucleophile without any exogeneous ligand.

A new method for direct synthesis of β-ketoenamines was developed by a BF3·OEt2-catalyzed cyclization of 1-iodoalkyne and α-keto acid followed by an amine-mediated ring-opening in one pot. Its metal-free conditions allowed the easy synthesis of those products bearing the transition metal-sensitive functional groups. Its three-component process achieved wide range of functionalized products.

A novel direct synthesis of 1,3-dioxo-substituted allenes was developed by copper(I)-catalyzed coupling of α-oxo-alkynes and α-oxo-diazos. It was a sequence of adding substrates-controlled method and the desired products were synthesized chemoselectively by adding α-oxo-alkyne terminally.

A silver-catalyzed ring-opening reaction of cyclopropanols with sulfonyl oxime ethers has been developed. The protocol was conducted under mild reaction conditions to provide a series of γ-keto oxime ethers with moderate to good yields. The reaction proceeded in a stereoselective manner for CF3-containing oxime ethers to provide a single stereoisomer, while an inseparable E and Z mixture was obtained for CN-containing oxime ethers. Mechanistic studies indicate that the reaction proceeded via a radical mechanism.

A highly reactive intermediate N-sulfonyl acetylketenimine was generated from an ynone-participated CuAAC/ring-opening method. Its unique structure allowed it to react with aryl carboxylic acids to give N-aroylsulfonamides via a novel Mumm-type rearrangement.

A highly reactive intermediate N-sulfonyl acetylketenimine was generated from a 3-butyn-2-one participating CuAAC/ring-opening method. Its high reactivity due to bearing two EWGs allowed us to offer the first example of a reaction between ketenimine and amide to synthesize N-sulfonyl amidines efficiently.

A general two-step one-pot synthesis process of ynones was developed by cycloaddition of α-keto acids and 1-iodoalkynes followed by a ring-opening reaction. Its easy conditions and novel mechanism endowed it with two distinctive advantages: iodine-atom bonded to C(sp2) remained intact and α-keto acids became a part of the triple bonds in ynones.

A new synthesis of diaryl sulfones is achieved from N,N'-disulfonylhydrazides and diaryliodonium salts. Its key advantage is that N,N'-disulfonylhydrazides carry out an efficient base-promoted evolution of nitrogen to generate in situ ammonium sulfinates with good solubility and high reactivity. N,N'-Disulfonylhydrazides prove to be an excellent synthetic equivalent of sulfinic acids and their salts with none of their drawbacks.

A novel ruthenium-catalyzed intramolecular cyclization of a nitrile and an azetidine was developed to achieve a one-step synthesis of the fused tricyclic 1H-2,3-dihydropyrimido[1,2-a]quinoline, which is the core skeleton for more than 100 natural pyoverdines and is also responsible for their fluorescence.

A novel silver-catalyzed decarboxylative acylation of α-oxo-carboxylic acids was developed, by which various 3-acyl quinoxalin-2(1H)-ones were synthesized by direct C-H bond acylation of quinoxalin-2(1H)-ones. In this method, α-oxo-carboxylic acids served as efficient acylating reagents to in situ generate the required active acyl radical. Its excellent chemoselectivity allowed the molecular diversity of 3-acyl quinoxalin-2(1H)-ones to be achieved by convenient functionalizations of both N1- and C3-positions.

An efficient synthesis of biphenyls was developed by a Cu(OTf)2-catalyzed direct arylation between an electron-rich arene and a diaryliodonium salt. The reaction went through a modified Friedel–Crafts reaction mechanism, in which Cu(OTf)2 served as both Lewis-acid catalyst and transition-metal catalyst to generate the aryl carbocation from the corresponding diaryliodonium salt.

A highly efficient synthesis of α-diazoketone was achieved by simply stirring the mixture of 1,3-diketone, TsN3, and MeNH2 in EtOH. It was a tandem reaction including a novel primary amine-catalyzed Regitz diazo transfer of 1,3-diketone and a novel primary amine-mediated C–C bond cleavage of 2-diazo-1,3-diketone.

A general and efficient aerobic oxidative hydroxylation of arylboronic acids promoted by benzoquinone in water was realized, and provided phenols in 72–95% yields for 20 examples. The main advantages of this protocol are the use of water as solvent in the presence of a catalytic amount of benzoquinone, and metal-free conditions.

The thermal Huisgen 1,3-dipolar cycloaddition of organic azides and alkynes to build 1,2,3-triazoles usually requires elevated temperatures and provides a mixture of regioisomers. The copper(I)-catalyzed azide–alkyne cycloaddition (CuAAC) and ruthenium(II)-catalyzed azide–alkyne cycloaddition (RuAAC) have been developed as powerful strategies for the regiospecific assembly of 1,4-disubstituted 1,2,3-triazoles and 1,5-disubstituted 1,2,3-triazoles, respectively. These reliable processes have quickly found many applications in organic synthesis, chemical biology, and materials science. Nevertheless, the contamination of heavy metals limits their potential application in the pharmaceutical industry. Several metal-free methods, including the azide–enamine cycloaddition, the condensation of azides with phosphonium ylides, and the addition of acetylide species to azides, have also been developed for the regiospecific synthesis of 1,2,3-triazoles. Considerable drawbacks, however, exist with these processes, such as poor functional-group tolerance or requiring functionalized substrates. Westermann recently reported an improved Sakai reaction to synthesize 1,4-disubstituted triazoles from primary amines and a,a-dichlorotosylhydrazones (Scheme 1a). This procedure is limited to the synthesis of 1,4-disubstituted regioisomers. Therefore, a general and metal-free procedure to synthesize 1,5-disubstituted triazoles from readily available substrates under mild reaction conditions is still of considerable interest. Herein we report the synthesis of the 1,5disubstituted triazoles 5 from a three-component reaction of aliphatic amines (1), propynones (2), and TsN3 by a Michael addition/deacylative diazo transfer/cyclization sequence (Scheme 1b). Theoretically, the enaminone compounds 4 may exist as three tautomers: the iminoenol 4a, iminoketone 4b, and ketoenamine 4c. The a-diazo iminoketone 7 and 1-tosyl triazole 8 could be obtained from the Regitz diazo transfer of 4b and 1,3-dipolar cycloaddition of 4c with TsN3, respectively. We assumed that, in the presence of suitable bases, 4a might react with TsN3 to give the a-diazoimine intermediate 6, which could further cyclize to afford the triazole 5 (Scheme 2).

A general and efficient palladium-catalyzed oxidative cross-coupling reaction of N-tosylhydrazones with indoles providing N-vinylindoles has been developed. The reaction proceeds smoothly with various indoles and N-tosylhydrazones in a stereocontrolled manner, and a wide variety of N-vinylindoles were obtained up to 99% yields for 26 examples.

Notable advantages of the optimized protocol are the use of water as solvent in the presence of benzoquinone as catalyst under metal free conditions.

The thermal Huisgen 1,3-dipolar cycloaddition of organic azides and alkynes to build 1,2,3-triazoles usually requires elevated temperatures and provides a mixture of regioisomers. The copper(I)-catalyzed azide–alkyne cycloaddition (CuAAC) and ruthenium(II)-catalyzed azide–alkyne cycloaddition (RuAAC) have been developed as powerful strategies for the regiospecific assembly of 1,4-disubstituted 1,2,3-triazoles and 1,5-disubstituted 1,2,3-triazoles, respectively. These reliable processes have quickly found many applications in organic synthesis, chemical biology, and materials science. Nevertheless, the contamination of heavy metals limits their potential application in the pharmaceutical industry. Several metal-free methods, including the azide–enamine cycloaddition, the condensation of azides with phosphonium ylides, and the addition of acetylide species to azides, have also been developed for the regiospecific synthesis of 1,2,3-triazoles. Considerable drawbacks, however, exist with these processes, such as poor functional-group tolerance or requiring functionalized substrates. Westermann recently reported an improved Sakai reaction to synthesize 1,4-disubstituted triazoles from primary amines and a,a-dichlorotosylhydrazones (Scheme 1a). This procedure is limited to the synthesis of 1,4-disubstituted regioisomers. Therefore, a general and metal-free procedure to synthesize 1,5-disubstituted triazoles from readily available substrates under mild reaction conditions is still of considerable interest. Herein we report the synthesis of the 1,5disubstituted triazoles 5 from a three-component reaction of aliphatic amines (1), propynones (2), and TsN3 by a Michael addition/deacylative diazo transfer/cyclization sequence (Scheme 1b). Theoretically, the enaminone compounds 4 may exist as three tautomers: the iminoenol 4a, iminoketone 4b, and ketoenamine 4c. The a-diazo iminoketone 7 and 1-tosyl triazole 8 could be obtained from the Regitz diazo transfer of 4b and 1,3-dipolar cycloaddition of 4c with TsN3, respectively. We assumed that, in the presence of suitable bases, 4a might react with TsN3 to give the a-diazoimine intermediate 6, which could further cyclize to afford the triazole 5 (Scheme 2).

The novel title oxidative Pd-catalyzed cross-coupling reaction tolerating a wide scope of functional groups is developed.