Palladium- and copper-mediated N-aryl bond formation reactions for the synthesis of biological active compounds

Photoelectrochemical Ni-catalyzed cross-coupling of aryl bromides with amine at ultra-low potential

Photoelectrochemical (PEC) cell is an ideal platform for organic transformation because of its green benefits and minimal energy consumption. As an emerging methodology, the reaction types of photoelectrocatalytic organic synthesis (PECOS) are limited to simple oxidation and C-H activation at current stage. Metal catalysis for the construction of C(sp2)-N bonds has not been touched yet in PECOS. We introduce here a PEC method that successfully engages Ni catalysis for the mild production of aniline derivatives. Experimental and computational investigations elucidate that the addition of photoanode-generated amine radical to Ni catalyst avoids the sluggish nucleophilic attack, enabling the reaction to proceed at an ultra-low potential (-0.4 V vs. Ag/AgNO3) and preventing the overoxidation of products in conventional electrochemical synthesis. This synergistic catalysis strategy exhibits good functional group tolerance and wide substrate scope on both aryl halides and amines, by which some important natural products and pharmaceutical chemicals have been successfully modified.

Electro-oxidative intermolecular CSP2-H amination of heteroarenes via proton-coupled electron transfer

A new electrochemical proton-coupled electron transfer method for the intermolecular CSP2-H amination of heteroarenes without oxidants, metal catalysts and external electrolytes has been developed. Various new N-containing heteroarenes were prepared in medium to high yields, and the indole-containing product could be converted into practical 2-oxindole by simple basic hydrolysis. Mechanistic investigation indicated that ester sulfonyl-substituted N-radicals could be formed by the combination of 2,6-lutidine and electrochemical oxidation, which is the key to achieve the desired chemoselectivity.

Aminative Suzuki-Miyaura coupling

The Suzuki-Miyaura and Buchwald-Hartwig coupling reactions are widely used to form carbon-carbon (C-C) and carbon-nitrogen (C-N) bonds, respectively. We report the incorporation of a formal nitrene insertion process into the Suzuki-Miyaura reaction, altering the products from C-C-linked biaryls to C-N-C-linked diaryl amines and thereby joining the Suzuki-Miyaura and Buchwald-Hartwig coupling pathways to the same starting-material classes. A combination of a bulky ancillary phosphine ligand on palladium and a commercially available amination reagent enables efficient reactivity across aryl halides and pseudohalides, boronic acids and esters, and many functional groups and heterocycles. Mechanistic insights reveal flexibility on the order of bond-forming events, suggesting potential for expansion of the aminative cross-coupling concept to encompass diverse nucleophiles and electrophiles as well as four-component variants.

Functionalization of Fe3O4@SiO2 nanoparticles with Cu(i)-thiosemicarbazone complex as a robust and efficient heterogeneous nanocatalyst for N-arylation of N-heterocycles with aryl halides

In this research, the functionalized silica-coated magnetite nanoparticles with Cu(i)-thiosemicarbazone complex (Fe3O4@SiO2-[CuL]) has been designed and synthesized as a magnetically retrievable nanocatalyst. Different techniques were employed to characterize the structure of Fe3O4@SiO2-[CuL] comprising FT-IR, FE-SEM, TEM, DLS, XRD, EDX, TGA, AAS, and VSM analysis. The catalytic performance of Fe3O4@SiO2-[CuL] was perused in Ullmann-type N-arylation of nucleobases, xanthines, and other N-heterocycles with diverse aryl halides which acquired the desired N-aryl products in good to excellent yields. Fe3O4@SiO2-[CuL] is a thermal and chemical stable, easy to prepare and recyclable, inexpensive, and ecofriendly catalyst that needs no additional additive or ligand as promoters. This catalyst could be separated without difficulty by a simple magnet and reused for at least seven sequential runs without a significant decline in its catalytic performance.

Understanding Formation and Roles of NiII Aryl Amido and NiIII Aryl Amido Intermediates in Ni-Catalyzed Electrochemical Aryl Amination Reactions

Ni-catalyzed electrochemical aryl amination (e-amination) is an attractive, emerging approach to building C-N bonds. Here, we report in-depth experimental and computational studies that examined the mechanism of Ni-catalyzed e-amination reactions. Key NiII-amine dibromide and NiII aryl amido intermediates were chemically synthesized and characterized. The combination of experiments and DFT calculations suggest (1) there is coordination of an amine to the NiII catalyst before the cathodic reduction and oxidative addition steps, (2) a stable NiII aryl amido intermediate is produced from the cathodic half-reaction, a critical step in controlling the selectivity between cross-coupling and undesired homo-coupling reaction pathways, (3) the diazabicycloundecene additive shifts the aryl halide oxidative addition mechanism from a NiI-based pathway to a Ni0-based pathway, and (4) redox-active bromide in the supporting electrolyte functions as a redox mediator to promote the oxidation of the stable NiII aryl amido intermediate to a NiIII aryl amido intermediate. Subsequently, the NiIII aryl amido intermediate undergoes facile reductive elimination to provide a C-N cross-coupling product at room temperature. Overall, our results provide new fundamental understandings about this e-amination reaction and guidance for further development of other Ni-catalyzed electrosynthetic reactions such as C-C and C-O cross-couplings.

Applications of palladium-catalyzed C-N cross-coupling reactions in pharmaceutical compounds

C-N cross-coupling bond formation reactions have become valuable approaches to synthesizing anilines and their derivatives, known as important chemical compounds. Recent developments in this field have focused on versatile catalysts, simple operation methods, and green reaction conditions. This review article presents an overview of C-N cross-coupling reactions in pharmaceutical compound synthesis reports. Selected examples of N-arylation reactions of various nitrogen-based compounds and aryl halides are defined for preparing pharmaceutical molecules.

Utilization of Aryl(TMP)iodonium Salts for Copper-Catalyzed N-Arylation of Isatoic Anhydrides: An Avenue to Fenamic Acid Derivatives and N,N'-Diarylindazol-3-ones

Herein, we report a general method for copper-catalyzed N-arylation of isatoic anhydrides with unsymmetrical iodonium salts at room temperature. The developed catalytic protocol is mild and operationally simple, and aryl(TMP)iodonium trifluoroacetate is employed as the arylating partner. The methodology offers the broad applicability of both structurally and electronically diverse aryl groups from aryl(TMP)iodonium salts to access N-arylated isatoic anhydrides in moderate to excellent yields (53-92%). Moreover, the substituted isatoic anhydrides are equally compatible with the protocol too. To demonstrate the synthetic utilities of the N-arylation process, we also report an alternative approach for biologically relevant fenamic acid derivatives and N,N'-diarylindazol-3-ones in a one-pot step economical system. In addition, the scale-up synthesis of flufenamic acid is also illustrated.

Regioselective C(sp2)-H imidation of arenes by redox neutral visible-light photocatalysis

We report herein a redox neutral visible light-induced regioselective C(sp²)-H imidation of electron-rich arenes and heteroarenes using conceptually designed redox-active 1 as a source of the N-centered imidyl radical. Structurally diverse aromatic imides were obtained in moderate to good yields. This methodology has been successfully employed for the late stage imidation of complex molecules and has also been applied towards the formal total synthesis of the marine natural products carpatamides A, B and D. It has further been shown that the generated imides can easily be converted to the corresponding anilines in situ directly.

Catalytically active atomically thin cuprate with periodic Cu single sites

Rational design and synthesis of catalytically active two-dimensional (2D) materials with an abundance of atomically precise active sites in their basal planes remains a great challenge. Here, we report a ligand exchange strategy to exfoliate bulk [Cu₄(OH)₆][O₃S(CH₂)₄SO₃] cuprate crystals into atomically thin 2D cuprate layers ([Cu₂(OH)₃]⁺). The basal plane of 2D cuprate layers contains periodic arrays of accessible unsaturated Cu(II) single sites (2D-CuSSs), which are found to promote efficient oxidative Chan-Lam coupling. Our mechanistic studies reveal that the reactions proceed via coordinatively unsaturated CuO₄(II) single sites with the formation of Cu(I) species in the rate-limiting step, as corroborated by both operando experimental and theoretical studies. The robust stability of 2D-CuSSs in both batch and continuous flow reactions, coupled with their recyclability and good performance in complex molecule derivatization, render 2D-CuSSs attractive catalyst candidates for broad utility in fine chemical synthesis.

Synthesis, Structure, and Biologic Activity of Some Copper, Nickel, Cobalt, and Zinc Complexes with 2-Formylpyridine N4-Allylthiosemicarbazone

A series of zinc(II) ([Zn(H₂O)(L)Cl] (1)), copper (II) ([Cu(L)Cl] (2), [Cu(L)Br] (3), [Cu₂(L)₂(CH₃COO)₂]·4H₂O (4)), nickel(II) ([Ni(HL)₂]Cl₂·H₂O (5)), and cobalt(III) ([Co(L)₂]Cl (6)) complexes were obtained with 2-formylpyridine N⁴-allylthiosemicarbazone (HL). In addition another two thiosemicarbazones (3-formylpyridine N⁴-allylthiosemicarbazone (HL^a) and 4-formylpyridine N⁴-allylthiosemicarbazone (HL^b)) have been obtained. The synthesized thiosemicarbazones have been studied using ¹H and ¹³C NMR spectroscopy, IR spectroscopy, and X-ray diffraction analysis. The composition and structure of complexes were studied using elemental analysis, IR and UV-Vis spectroscopies, molar conductivity, and magnetic susceptibility measurements. Single crystal X-ray diffraction analysis elucidated the structure of thiosemicarbazones HL, HL^a, and HL^b, as well as complexes 4 and 5. The antiproliferative properties of these compounds toward a series of cancer cell lines (HL-60, HeLa, BxPC-3, RD) and a normal cell line (MDCK) have been investigated. The nickel complex shows high selectivity (SI > 1000) toward HL-60 cell line and is the least toxic. The zinc complex shows the highest selectivity toward RD cell line (SI = 640). The copper complexes (2–4) are the most active molecular inhibitors of proliferation of cancer cells, but exhibit not such a high selectivity and are significantly more toxic. Zinc and copper complexes manifest high antibacterial activity. It was found that calculated at B3LYP level of theory different reactivity descriptors of studied compounds strongly correlate with their biological activity.

Complementary catalysis and analysis within solid state additively manufactured metal micro flow reactors

Additive Manufacturing is transforming how researchers and industrialists look to design and manufacture chemical devices to meet their specific needs. In this work, we report the first example of a flow reactor formed via the solid-state metal sheet lamination technique, Ultrasonic Additive Manufacturing (UAM), with directly integrated catalytic sections and sensing elements. The UAM technology not only overcomes many of the current limitations associated with the additive manufacturing of chemical reactionware but it also significantly increases the functionality of such devices. A range of biologically important 1, 4-disubstituted 1, 2, 3-triazole compounds were successfully synthesised and optimised in-flow through a Cu mediated Huisgen 1, 3-dipolar cycloaddition using the UAM chemical device. By exploiting the unique properties of UAM and continuous flow processing, the device was able to catalyse the proceeding reactions whilst also providing real-time feedback for reaction monitoring and optimisation.

A Combined Spectroscopic and Computational Study on the Mechanism of Iron-Catalyzed Aminofunctionalization of Olefins Using Hydroxylamine Derived N-O Reagent as the "Amino" Source and "Oxidant"

Herein, we study the mechanism of iron-catalyzed direct synthesis of unprotected aminoethers from olefins by a hydroxyl amine derived reagent using a wide range of analytical and spectroscopic techniques (Mössbauer, Electron Paramagnetic Resonance, Ultra-Violet Visible Spectroscopy, X-ray Absorption, Nuclear Resonance Vibrational Spectroscopy, and resonance Raman) along with high-level quantum chemical calculations. The hydroxyl amine derived triflic acid salt acts as the “oxidant” as well as “amino” group donor. It activates the high-spin Fe(II) (S_t = 2) catalyst [Fe(acac)₂(H₂O)₂] (1) to generate a high-spin (S_t = 5/2) intermediate (Int I), which decays to a second intermediate (Int II) with S_t = 2. The analysis of spectroscopic and computational data leads to the formulation of Int I as [Fe(III)(acac)₂-N-acyloxy] (an alkyl-peroxo-Fe(III) analogue). Furthermore, Int II is formed by N–O bond homolysis. However, it does not generate a high-valent Fe(IV)(NH) species (a Fe(IV)(O) analogue), but instead a high-spin Fe(III) center which is strongly antiferromagnetically coupled (J = −524 cm^–1) to an iminyl radical, [Fe(III)(acac)₂-NH·], giving S_t = 2. Though Fe(NH) complexes as isoelectronic surrogates to Fe(O) functionalities are known, detection of a high-spin Fe(III)-N-acyloxy intermediate (Int I), which undergoes N–O bond cleavage to generate the active iron–nitrogen intermediate (Int II), is unprecedented. Relative to Fe(IV)(O) centers, Int II features a weak elongated Fe–N bond which, together with the unpaired electron density along the Fe–N bond vector, helps to rationalize its propensity for N-transfer reactions onto styrenyl olefins, resulting in the overall formation of aminoethers. This study thus demonstrates the potential of utilizing the iron-coordinated nitrogen-centered radicals as powerful reactive intermediates in catalysis.

6-Iodopurine as a Versatile Building Block for RNA Purine Architecture Modifications

Natural modified bases in RNA were found to be indispensable for basic biological processes. In addition, artificial RNA modifications have been a versatile toolbox for the study of RNA interference, structure, and dynamics. Here, we present a chemical method for the facile synthesis of RNA containing C⁶-modified purine. 6-Iodopurine, as a postsynthetic building block with high reactivity, was used for metal-free construction of C-N, C-O, and C-S bonds under mild conditions and C-C bond formation by Suzuki-Miyaura cross-coupling. Our strategy provides a convenient approach for the synthesis of various RNA modifications, especially for oligonucleotides containing specific structures.

Solid-State C-N Cross-Coupling Reactions with Carbazoles as Nitrogen Nucleophiles Using Mechanochemistry

The palladium-catalyzed solid-state C-N cross-coupling of carbazoles with aryl halides via a high-temperature ball-milling technique has been reported. This reaction allowed simple, fast, and efficient synthesis of N-arylcarbazole derivatives in good to excellent yields without the use of large amounts of organic solvents in air. Importantly, the developed solid-state coupling approach enabled the cross-coupling of poorly soluble aryl halides with large polyaromatic structures that are barely reactive under conventional solution-based conditions.

C–N coupling reactions with arenes through C–H activation: the state-of-the-art versus the principles of green chemistry

Herein, we discuss the state-of-the-art in arene C–N coupling through C–H activation and to what extent it complies with the principles of green chemistry, with a focus on heterogeneously catalysed systems.

Decarboxylative Amination of Benzoic Acids Bearing Electron-Donating Substituents and Non-Activated Amines

Efficient methods for decarboxylative activation of benzoic acids into great valuable products are highly sought after. Here we report a highly desirable and straightforward decarboxylative amination of readily available benzoic...

Recent Advances in the Tandem Copper-Catalyzed Ullmann-Goldberg N-Arylation–Cyclization Strategies

N‒Aryl bond formation under copper catalysis has been playing a pivotal role and has been extensively used as a key step in the total syntheses of several therapeutic molecules. The...

Development of Anthrazoline Photocatalyst for Promoting Amination and Amidation Reactions

In this work, we report the synthesis, optical and electrochemical properties of a series of organophotocatalysts bearing anthrazoline framework, as well as demonstrate their catalytic competencies in promoting C-N bond...

Nickel-Catalyzed Paired Electrochemical Cross-Coupling of Aryl Halides with Nucleophiles

Electrochemistry has recently gained increased attention as a versatile strategy for achieving challenging transformations at the forefront of synthetic organic chemistry. However, most electrochemical transformations only employ one electrode (anodic oxidation or cathodic reduction) to afford the desired products, while the chemistry that occurs at the counter electrode yields stoichiometric waste. In contrast, paired electrochemical reactions can synchronously utilize the anodic and cathodic reactions to deliver the desired product, thus improving the atom economy and energy efficiency of the electrolytic process. This review gives an overview of recent advances in nickel-catalyzed paired electrochemical cross-coupling reactions of aryl/alkenyl halides with different nucleophiles.

1 Introduction

2 Nickel-Catalyzed Cross-Coupling Reactions

2.1 C–C Bond Formation

2.2 C–N Bond Formation

2.3 C–S/O Bond Formation

2.4 C–P Bond Formation

3 Conclusion

Design and synthesis of Fe3O4@SiO2@KIT-6@DTZ-Pd0 as a new and efficient mesoporous magnetic catalyst in carbon-carbon cross-coupling reactions

In this paper, a new type of mesoporous material based on KIT-6 has been introduced. In this aim, magnetic Fe3O4 nanoparticles and mesoporous silica KIT-6 have been combined to obtain mesoporous MNPs. The prepared magnetic mesoporous catalyst has been applied in different carbon-carbon cross-coupling reactions including Mizoroki-Heck, Suzuki-Miyaura, and Stille reactions. This magnetic mesoporous compound is characterized by various techniques including FT-IR, BET, VSM, SEM, XRD, and TGA.

High Turnover Pd/C Catalyst for Nitro Group Reductions in Water. One-Pot Sequences and Syntheses of Pharmaceutical Intermediates

Commercially available Pd/C can be used as a catalyst for nitro group reductions with only 0.4 mol % Pd loading. The reaction can be performed using either silane as a transfer hydrogenating agent or simply a hydrogen balloon (∼1 atm pressure). With this technology, a series of nitro compounds was reduced to the desired amines in high chemical yields. Both the catalyst and surfactant were recycled several times without loss of reactivity.

Chemoselective, Scalable Nickel-Electrocatalytic O-Arylation of Alcohols

The formation of aryl-alkyl ether bonds through cross coupling of alcohols with aryl halides represents a useful strategic departure from classical SN 2 methods. Numerous tactics relying on Pd-, Cu-, and Ni-based catalytic systems have emerged over the past several years. Herein we disclose a Ni-catalyzed electrochemically driven protocol to achieve this useful transformation with a broad substrate scope in an operationally simple way. This electrochemical method does not require strong base, exogenous expensive transition metal catalysts (e.g., Ir, Ru), and can easily be scaled up in either a batch or flow setting. Interestingly, e-etherification exhibits an enhanced substrate scope over the mechanistically related photochemical variant as it tolerates tertiary amine functional groups in the alcohol nucleophile.

Recent developments in decarboxylative C(aryl)-X bond formation from (hetero)aryl carboxylic acids

Decarboxylative coupling reactions using readily available (hetero)aryl carboxylic acids are a highly efficient approach for the formation of new C-C and C-X bonds. These decarboxylative coupling reactions eliminate CO2 as a by-product, resulting in a greener and environmentally more benign approach than conventional coupling reactions. In this review, we summarize the recent developments in ipso-decarboxylative C-X (X = O/N/halo/S/Se/P/CN) bond formations using (hetero)aryl carboxylic acids. Furthermore, we highlight the current limitations and future research opportunities of aryl-decarboxylative coupling reactions.

Iron-catalyzed cross-dehydrogenative C–H amidation of benzofurans and benzothiophenes with anilines

An efficient iron-catalyzed radical cross-dehydrogenative aromatic C–H amidation provides a straightforward access to structurally diverse diarylamine derivatives incorporating benzofuran/benzothiophene motifs.

Synthesis and in vitro anticancer activities of substituted N-(4'-nitrophenyl)-l-prolinamides

Prolinamides are present in secondary metabolites and have wide-ranging biological properties as well as antimicrobial and cytotoxic activities. N-(4'-substituted phenyl)-l-prolinamides 4a-4w were synthesized in two steps, starting from the condensation of p-fluoronitrobenzene 1a-1b with l-proline 2a-2b, under aqueous-alcoholic basic conditions to afford N-aryl-l-prolines 3a-3c, which underwent amidation via a two-stage, one-pot reaction involving SOCl2 and amines, to furnish l-prolinamides in 20-80% yield. The cytotoxicities of 4a-4w against four human carcinoma cell lines (SGC7901, HCT-116, HepG2 and A549) were evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay; with good tumour inhibitory activities (79.50 ± 1.24%-50.04 ± 1.45%) against HepG2. 4a exhibited the best anti-tumour activity against A549 with percentage cell inhibition of 95.41 ± 0.67% at 100 µM. Likewise, 4s (70.13 ± 3.41%) and 4u (83.36 ± 1.70%) displayed stronger antineoplastic potencies against A549 than the standard, 5-fluorouracil (64.29 ± 2.09%), whereas 4a (93.33 ± 1.36%) and 4u (81.29 ± 2.32%) outperformed the reference (81.20 ± 0.08%) against HCT-116. SGC7901 showed lower percentage cell viabilities with 4u (8.02 ± 1.54%) and 4w (27.27 ± 2.38%). These results underscore the antiproliferative efficacies of l-prolinamides while exposing 4a and 4u as promising broad-spectrum anti-cancer agents. Structure-activity relationship studies are discussed.

Copper-catalyzed direct amination of benzylic hydrocarbons and inactive aliphatic alkanes with arylamines

A new synthetic method toward direct C-N bond formation through saturated C-H amination of benzylic hydrocarbons and inactive aliphatic alkanes with primary aromatic amines under an inexpensive catalyst/oxidant (Cu/DTBP) system has been developed. Both aminopyridines and anilines could react smoothly with primary and secondary benzylic C-H substrates or cyclohexane to form the corresponding aromatic secondary amines in moderate to good yields. This protocol has the advantages of wide functional group tolerance and use of readily available raw materials.

C-N Coupling of DNA-Conjugated (Hetero)aryl Bromides and Chlorides for DNA-Encoded Chemical Library Synthesis

DNA-encoded chemical library (DECL) screens are a rapid and economical tool to identify chemical starting points for drug discovery. As a robust transformation for drug discovery, palladium-catalyzed C–N coupling is a valuable synthetic method for the construction of DECL chemical matter; however, currently disclosed methods have only been demonstrated on DNA-attached (hetero)aromatic iodide and bromide electrophiles. We developed conditions utilizing an N-heterocyclic carbene–palladium catalyst that extends this reaction to the coupling of DNA-conjugated (hetero)aromatic chlorides with (hetero)aromatic and select aliphatic amine nucleophiles. In addition, we evaluated steric and electronic effects within this catalyst series, carried out a large substrate scope study on two representative (hetero)aryl bromides, and applied this newly developed method within the construction of a 63 million-membered DECL.

One-pot ortho-amination of aryl C-H bonds using consecutive iron and copper catalysis

A one-pot approach for ortho-coupling of arenes with non-actived N-nucleophiles has been developed using sequential iron and copper catalysis. Regioselective ortho-activation of anisoles, anilines and phenols was achieved through iron(iii) triflimide catalysed iodination, followed by a copper(i)-catalysed, ligand-assisted coupling reaction with N-heterocycle, amide and sulfonamide-based nucleophiles. The synthetic utility of this one-pot, two-step method for the direct amination of ortho-aryl C-H bonds was demonstrated with the late-stage functionalisation of 3,4-dihydroquinolin-2-ones. This allowed the preparation of a TRIM24 bromodomain inhibitor and a series of novel analogues.

Electrochemical oxidation induced intermolecular aromatic C-H imidation

The dehydrogenative aryl C-H/N-H cross-coupling is a powerful synthetic methodology to install nitrogen functionalities into aromatic compounds. Herein, we report an electrochemical oxidation induced intermolecular cross-coupling between aromatics and sulfonimides with high regioselectivity through N-radical addition pathway under external-oxidant-free and catalyst-free conditions. A wide variety of arenes, heteroarenes, alkenes and sulfonimides are applicable scaffolds in this transformation. In addition, aryl sulfonamides or amines (aniline derivatives) can be obtained through different deprotection process. The cyclic voltammetry mechanistic study indicates that the N-centered imidyl radicals are generated via proton-coupled electron transfer event jointly mediated by tetrabutylammonium acetate and anode oxidation process.

The dehydrogenative C-H/N-H cross-coupling serves to install nitrogen functionalities into arenes with the highest atom economy. Here, the authors report an electrochemical cross-coupling between aromatics and sulfonimides through an N-radical addition pathway under oxidant- and catalyst-free conditions.

Synthetic Approaches for C-N Bonds by TiO2 Photocatalysis

Nitrogen-containing organic compounds possess the most important status in drug molecules and agricultural chemicals. More than 80% currently used drugs have at least a C-N bond. The green and mild methodology to prepare diverse C-N bonds to replace traditional harsh preparation protocols is always a hotspot in modern synthetic chemistry. TiO₂-based nanomaterials, considered as environmentally benign, stable, and powerful photocatalysts, have recently been applied in some certain challenging organic synthesis including construction of useful C-N compounds under mild conditions that are impossible to complete by conventional catalysis. This mini review would present state-of-the-art paragon examples of TiO₂ photocatalyzed C-N bond formations. The discussion would be divided into two main sections: (1) N-alkylation of amines and (2) C-N formation in heterocycle synthesis. Especially, the mechanism of TiO₂ photocatalytic C-N bond formation through activating alcohol into C=O by photo-induced hole followed by C=NH-R formation and finally hydrogenating C=NH-R into C-N bonds by combination of photo-induced electron/H⁺ assisted with loaded-Pt would be covered in detail. We believe that the mini-review will bring new insights into TiO₂ photocatalysis applied to construct challenging organic compounds through enabling photo-induced hole and electron in a concerted way on coupling two substrate molecules together with respect to their conventionally independent catalysis behavior.