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A photoredox/nickel-catalyzed selective 1,4-arylsulfonation of 1,3-enynes to access structurally diverse sulfone-containing allenes has been established with low catalyst loading.

A synthesis of trifluoromethylated thioethers via Ni-catalyzed reductive C–S coupling has been established, exhibiting broad substrate scope and high efficiency.

An exclusively regioselective hydrocyanation of monofluoroalkenes has been developed, with which a series of aliphatic quaternary α-fluoronitriles were synthesized in a facile and efficient manner. This novel method is featured with mild conditions, good functional groups compatibilities, and high reactivity.

The first example of copper-catalyzed ring-opening, enantioselective arylation of cyclic ketoxime esters to access ω,ω-diaryl alkyl nitriles has been developed in high yield (up to 92% yield) with excellent enantioselectivity (up to 91% ee). Side-arm bis(oxazoline) ligand plays a significant role in this asymmetric catalytic transformation, which provides an efficient route to construct diverse chiral ω,ω-diaryl alkyl nitriles. Synthetic utility has also been demonstrated in the further derivatization of the ω,ω-diaryl alkyl nitrile to the corresponding amide.

A facile and efficient approach for the synthesis of the CF3-containing dioxodibenzothiazepines has been developed via copper-catalyzed trifluoromethylation/cyclization of alkynes utilizing a radical relay strategy. This method has demonstrated low catalyst loading, high regiocontrol, and broad scope under mild conditions. Good compatibility for the N-protecting group, gram-scale experiment, and further derivation of product prove the versatility of this transformation.

The cross-coupling of C-N bond directly from inert C-H bonds is an ideal approach to synthesize saturated azacycles due to its high efficiency and atom economy. In this article, a copper-catalyzed intramolecular amination via the cross coupling of C(sp3)-H and N-H bonds of secondary amine has been reported, which exhibit excellent chemo- and regioselectivity, extensive substrate scope, and functional group tolerance in good to excellent yield, offering an efficient pathway to build nitrogen-containing heterocycle skeletons.

Circularly polarized light (CPL)-triggered enantioselective thiol–ene reactions, which combine absolute asymmetric synthesis with click reactions, enable facile synthesis of optically active poly(thioether) directly from a racemic monomer. However, the enantioselectivity is low and the challenge of producing highly asymmetrical poly(thioether) with distinct circularly polarized luminescence has not been met to date. Herein, we show that the poor enantioselectivity can be largely attributed to the inevitable racemization of thiyl radicals during the growth cycle, and more importantly, it can be remedied by addition of achiral hydrogen atom donors (HAD). The enhancement in enantioselectivity of CPL-triggered thiol–ene reactions can be experimentally controlled by varying the reaction kinetics without introducing any chiral inducer other than CPL. A maximum excess of enantiomeric units (∼20%) in the final polymer chains could be obtained, and so-formed optically active poly(thioether) exhibited not only clusterization-triggered emission (CTE), but also fascinating circularly polarized luminescence for the first time.

A Rh(III)-catalyzed C-H arylation reaction of N-nitrosoanilines has been developed in which arylboronic acids were used as arylation reagents. It provides an efficient strategy for the synthesis of N-nitroso-[1,1'-biphenyl]-2-amine, which is an important starting material for the synthesis of N-hetero biaryl compounds, such as 2-amine-1,1'-biphenyl, carbazole, phenanthridone. This protocol can be applied to various N-alkyl substituted N-nitrosoanilines and N-nitrosoanilines with substituents on the phenyl ring. Arylboronic acids with both electron-donating and electron-withdrawing groups are tolerated.

The first example of the Pd(II)-catalyzed enantioselective amination of aryl C-H bonds is reported. The key to the successful realization of this asymmetric catalytic transformation was the identification of mono-N-protected α-amino-O-methylhydroxamic acid (MPAHA) ligands, which promote reactivity under mild conditions and control enantioselectivity. The counteranions in the solvent medium, hexafluoroacetylacetate and acetate, were also found to play key roles in stereocontrol and reactivity enhancement.

The highly efficient copper-catalyzed enantioselective alkynylation of the remote C(sp3)–H bond on linear primary sulfonamides is presented here using a radical relay strategy. The chiral box–coppe...

The first example of a visible light-mediated atom transfer radical addition reaction of (phenylsulfonyl)difluoromethyl iodide to styrenes has been reported. By simply tuning the organic or inorganic bases in the reaction system, both ATRA and heck-type products could be afforded with high selectivity. This method has demonstrated mild conditions, high catalytic reactivity, excellent chemoselectivity and a broad substrate scope. Besides, it offers a new solution for difunctionalization of alkenes to synthesize diverse difluoromethylated molecules after a simple work-up.

With an iron catalyst playing dual roles as a radical initiator and terminator, we report a selective remote C–H functionalization to access δ-azido sulfonamides through a radical relay process. The reaction of N-fluorosulfonamide furnishes the corresponding products in excellent yields with high regioselective control. The key to success is the highly efficient iron-mediated redox azido transfer to the in situ generated carbon radical. The products provide incentives for drug discovery and ligand designs.

A nickel-catalyzed difluoroalkylation of α-C-H bonds of aryl ketones to furnish highly stereo-defined tetrasubstituted monofluoroalkenes or quaternary alkyl difluorides from secondary or tertiary ketones, respectively, has been established. Mechanistic investigations indicated that these C-H fluoroalkylations proceed via a Ni(i)/Ni(iii) catalytic cycle. An obvious fluorine effect was observed in the reaction, and this reaction has demonstrated high stereoselectivity, mild conditions, and broad substrate scopes, thus enabling the late-stage fluoroalkylation of bioactive molecules. This method offers a solution for expedient construction of monofluoroalkenes from readily available materials, and provides an efficient approach for the synthesis of bioactive fluorinated compounds for the discovery of lead compounds in medicinal chemistry.

Enantioselective synthesis of tetrahydroisoquinolines bearing an all-carbon quaternary stereogenic center, was achieved via asymmetric C–H activation with high enantioselectivities (up to 93% ee). Fair substrate tolerance was indicated throughout the scope investigation and no evident loss of enantioselectivity was exhibited in late-stage derivatization. This study provides incentives for the construction of diverse chiral isoquinoline derivatives, which are prevalent among pharmaceuticals, natural products, etc.

A copper-catalyzed dichloromethylazidation of alkenes using commercially available BrCCl2H as a stoichiometric dichloromethylating reagent has been reported. Mechanistic studies indicated that a dichloromethyl radical was involved in the catalytic cycle. This transformation has demonstrated mild conditions, high reactivity, excellent functional-group tolerance, and a broad substrate scope, and thus it has offered a new solution for difunctionalization of alkenes to make diverse transformable dichloromethylated molecules.

A palladium-catalyzed, amine-directed C(sp2)–H carbonylation of α,α-disubstituted benzylamine under 1 atm of CO for the facile synthesis of sterically hindered benzolactam has been developed. The key to success is the use of 2,2,6,6-tetramethyl-1-piperidinyloxy as the crucial sole oxidant. The synthetic utility of this transformation has been demonstrated by the first concise synthesis of the natural product spiropachysin-20-one.

A novel palladium-catalyzed C-H formylation of electron-rich N-, O-, and S-containing heteroarenes has been developed. The key to success is that the commercially available BrCHCl2 was used as a stoichiometric carbonyl source. Mechanistic investigations indicated that different from the known Reimer-Tiemann reaction, this net C-H formylation proceeded through an electrophilc radical-type path.

An efficient nickel-catalyzed reductive relay cross-coupling of internal alkenes with alkyl (or aryl) halides has been developed. This method has demonstrated broad substrate scope, mild reaction conditions and excellent terminal-selectivity. Moreover, this efficient strategy could be applied to the terminal-selective alkylation of isomeric mixtures of internal alkenes.

An efficient nickel-catalyzed Heck-type reaction between styrenes and fluoroalkyl iodine has been developed. This novel transformation has demonstrated a broad substrate scope, mild reaction conditions and excellent E-stereoselectivity. This efficient synthetic method has been applied to the late-stage monofluoroacetation of biologically active molecules. Mechanistic investigations indicate that a monofluoroalkyl radical is involved in the catalytic cycle.

A nickel-catalyzed direct difluoromethylation of aryl boronic acids has been developed for the first time, demonstrating good efficiency, mild conditions, and good functional-group compatibility. The key to success is the combination of different kinds of readily available nitrogen and phosphine ligands with a nickel source, which can generate a variety of easily tunable catalysts in situ to promote the difluoromethylation of a broad scope of aryl boronic acids.

A neutral metal-free system for the head-to-tail dimerization of electron-rich alkenes with stoichiometric amount of BrCCl2H and NaI is reported. This reaction proceeds under mild conditions with high efficiency and broad scope.

An oxidative cleavage of C–C double bonds of enamides promoted by hypervalent iodine(III)/TMSN3 under an air atmosphere is developed. This reaction provides a new approach to construct various cyanobenzamides, which offers further synthetic potential for the preparation of industrial and pharmaceutical nitrogen- and oxygen-containing molecules, and exhibits good functional group tolerance, broad substrate scope and mild conditions.

A copper-catalyzed enantioselective 1,5-cyanotrifluoromethylation of vinylcyclopropanes has been developed using a radical relay strategy. This asymmetric reaction has demonstrated high enantioselective control, broad substrate scope, and mild conditions. Initiated by the

The first example of a nickel-catalyzed C–H trifluoromethylation of electron-rich heteroarenes, including imidazopyridines, indoles and thiophenes, has been developed with the commercially available and relatively inexpensive industrial raw material iodotrifluoromethane (CF3I) as the trifluoromethylating reagent. The synthetic potential of this method is demonstrated by its successful application to the direct trifluoromethylation of the biologically active molecules melatonin and zolmitriptan.

The first example of copper-catalyzed decarboxylative atom transfer radical addition of alkynyl carboxylic acids has been developed with a readily available fluoroalkyl halide. This novel protocol has demonstrated a unique difunctionalization of nonterminal alkynes with a broad substrate scope and excellent functional-group tolerance. Mechanistic investigations revealed that the catalytic cycle was initiated by the attack of a difluoroalkyl radical to an in situ generated alkynylcopper species.

A novel electrophilic trifluoromethylthiolation reaction system has been developed with AgSCF3 used directly as the SCF3 source, in the presence of KI/K2S2O8/I2. Various N-benzylindoles have been trifluoromethylthiolated successfully with this system, and the mechanism of investigation showed an electrophilic reagent was generated in situ.

A novel palladium-catalyzed C-7 selective CH carbonylation of indolines with carbon monoxide for an expedient synthesis of pyrroloquinazolinediones, a structural motif with great potential in biologically active compounds, has been developed. Oxidation of the pyrroloquinazolinedione with 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) could easily afford the corresponding indole-based derivative in excellent yield.

A rhodium(III)-catalyzed direct C-H alkynylation of a wide range of N-methylsulfoximines with (bromoethynyl)triisopropylsilane has been developed. This protocol is compatible with both (S,S)-diaryl sulfoximines and (S,S)-alkyl aryl sulfoximines, and shows mild conditions, and good functional group tolerance. The synthetic utility of this method has been demonstrated by subsequent various transformations of the products.

A novel Pd-catalyzed direct C(sp(3))-H carbonylation of alkylamines for the synthesis of γ-lactams and γ-amino acids has been developed, in which TEMPO was used as the crucial sole oxidant. The synthetic prospect was demonstrated by the concise total synthesis of rac-Pregbalin.

Aryl boronic acids can be monofluoromethylated under nickel catalysis. The utility of this method is demonstrated by the monofluoromethylation of a borylated and acyl-protected derivative of the statin drug ezetimibe. Mechanistic investigations indicate that a fluoromethyl radical is involved in the Ni(I)/Ni(III) catalytic cycle.

A palladium(II)-catalyzed C-H arylation directed by tetrazole, a metabolically stable surrogate for the carboxylic acid group in drug design, has been developed. Excellent mono-/di-selectivity was achieved through adjustment of the protecting site on the tetrazole ring. The synthetic utility of this new transformation was demonstrated in the concise total synthesis of Losartan.

A novel radical [1,3]-nitrogen shift catalyzed by copper diacetate under 1 atm of oxygen atmosphere for the construction of a diversity of indole structure motifs from α,α-disubstituted benzylamine has been developed, in which oxygen was used as a clean terminal oxidant and water was produced as the only byproduct. Of particular note is five inert bonds were cleaved, and two C-N bonds and one C-C double bond were constructed in one pot during this transformation. This unique method demonstrated broad application prospect for late-stage modification of biologically active natural products and drugs. Mechanistic investigations indicate that a unique 4-exo-trig cyclization of an aminyl radical to phenyl ring was involved in the catalytic cycle.

A novel method for visible-light photoredox-catalyzed difluoromethylation of electron-rich N-, O-, and S-containingheteroarenes under mild reaction conditions is developed. Mechanistic investigation indicates that the net C-H difluoromethylation proceeds through an electrophilic radical-type pathway.

Palladium-catalyzed CF bond formation via directed CH activation has recently emerged as a significant method to introduce fluorine atoms into organic molecules in an atom- and step-economical path. At the interface between fluorine chemistry and synthetic organic chemistry, the development of direct fluorinations of the CH bond remains sluggish, due to the major challenge of reductive elimination to afford the CF bond. One strategy is to oxidize palladium(II) species to more electron-deficient palladium(IV or III) fluorides to promote the CF bond forming reductive elimination, which opens up palladium-catalyzed CH fluorination as a powerful transformation. This focused review gives a brief summary of the mere handful of examples, including C(sp2)F and C(sp3)F bond formations, in this field so far.

An iron-catalyzed aryldifluoromethylation of activated alkenes under mild reaction conditions has been developed, which is a rare example where a cosolvent is used to improve the reaction yield along with Fenton's reagent and thus provides an economic and green method for the synthesis of a variety of difluoromethylated oxindoles. Preliminary mechanistic investigations indicate a radical addition path.

A rhodium(III)-catalyzed oxidative CH olefination directed by Weinreb amides, a class of well developed versatile building blocks in organic synthesis, has been developed with air as the terminal oxidant. The reactions proceed with excellent reactivity, good functional group tolerance and high yields.

A practical Pd(II)/Pd(IV)-catalyzed carboxyl-directed C-H activation/C-O cyclization to construct biaryl lactones has been developed. The synthetic utility of this new reaction was demonstrated in an atom-economical and operationally convenient total synthesis of the natural product cannabinol from commercially available starting materials, with the newly developed method used for two key steps.

The first example of nickel-catalyzed monofluoroalkylation of arylsilanes has been developed with readily available fluoroalkyl halides. This novel transformation has demonstrated high reactivity, broad substrate scope, excellent functional group tolerance, and mild reaction conditions. The selective activation of a relatively inert C–Si bond for slow release of aryl carbanion is the key reason for reducing the amount of arylmetal species, which makes this method more promising for fluorine-containing modification of complex bioactive molecules. Mechanistic investigations indicate that a free fluoroalkyl radical is involved in this catalytic cycle.

The first example of nickel-catalyzed decarboxylative fluoroalkylation of α,β-unsaturated carboxylic acids has been developed with commonly available fluoroalkyl halides. This novel transformation has demonstrated broad substrate scope, excellent functional-group tolerance, mild reaction conditions, and excellent stereoselectivity. Mechanistic investigations indicate that a fluoroalkyl radical is involved in the catalytic cycle.

Pd-catalyzed highly para-selective C-H arylation of monosubstituted arenes (including toluene) is developed for the first time using an F(+) reagent as a bystanding oxidant. This finding provides a new retrosynthetic disconnection for para-substituted biaryl synthesis via C-H/C-H cross-coupling.

The first example of nickel-catalyzed decarboxylative fluoroalkylation of α,β-unsaturated carboxylic acids has been developed with commonly available fluoroalkyl halides. This novel transformation has demonstrated broad substrate scope, excellent functional-group tolerance, mild reaction conditions, and excellent stereoselectivity. Mechanistic investigations indicate that a fluoroalkyl radical is involved in the catalytic cycle.

A novel Pd-catalyzed direct C(sp3)–H carbonylation of alkylamines for the synthesis of γ-lactams and γ-amino acids has been developed, in which TEMPO was used as the crucial sole oxidant. The synthetic prospect was demonstrated by the concise total synthesis of rac-Pregbalin.

The reaction of phenylsulfonyl or ester activated monofluoro monohalomethanes with arylboronic acids is achieved in the presence of a nickel catalyst to yield the corresponding fluoromethylaryl derivatives.

The development of heterogeneous chiral catalysts for enantioselective reactions is highly desirable in order to overcome some drawbacks of homogeneous catalysts. Different from the conventional approaches by using various types of supports or biphasic systems for the recovery and reuse of homogeneous catalysts, a conceptually new strategy for heterogenization of homogeneous chiral catalysts, that is, a "self-supporting" approach, has been developed to use homochiral metal-organic coordination polymers generated by the self-assembly of chiral multitopic ligands with metal ions, and thus obviates the use of any support. In this concept article, the success of this "self-supporting" strategy will be exemplified in heterogeneous catalysis of asymmetric carbonyl-ene, sulfoxidation, epoxidation, and asymmetric hydrogenation reactions.

A new strategy for the heterogenization of chiral titanium complexes was developed by the in situ assembly of bridged multitopic BINOL ligands with [Ti(OiPr)4] without using a support. The assembled heterogeneous catalysts (self-supported) showed excellent enantioselectivity in both the carbonyl-ene reaction of alpha-methylstyrene with ethyl glyoxylate (up to 98 % ee) and the oxidation of sulfides (up to >99 % ee). The catalytic performance of these heterogeneous catalytic systems was comparable or even superior to that attained with their homogeneous counterparts. The spacers between the two BINOL units of the ligands in the assembled catalysts had significant impact on the enantioselectivity of the carbonyl-ene reaction. This demonstrates the importance of the supramolecular structures of the assemblies on their catalytic behavior. In the catalysis of sulfoxidation, the self-supported heterogeneous titanium catalysts were highly stable and could be readily recycled and reused for over one month (at least eight cycles) without significant loss of activity and enantioselectivity (up to >99.9 % ee). The features of these self-supported catalysts, such as facile preparation, robust chiral structure of solid-state catalysts, high density of the catalytically active units in the solids, as well as easy recovery and simple recycling, are particularly important in developing methods for the synthesis of optically active compounds in industrial processes.