Oxidation-induced <Emphasis Type="Italic">ortho</Emphasis>-selective C–H bond functionalization of 2-naphthylamine derivative

Selective C–H bond functionalization has been emerged as a versatile strategy for the construction of new chemical bonds. In the past decades, the directing group (DG)-assisted C–H bond activation has been developed as one of the most efficient methods for selective C–H functionalization. Although a great progress has been made by utilizing this traditional method, developing new strategy for selective C–H bond functionalization is still highly demanded. Hence, a novel oxidation-induced C–H bond functionalization method was demonstrated in this work. By this new method, ortho-C(sp₂)–H chlorination of N-substituted 2-naphthylamine was realized in a highly selective manner.     

Palladium-catalyzed ortho-selective C–H bond chlorination of aromatic ketones

A palladium-catalyzed ortho-selective C–H bond chlorination reaction for the preparation of 2-chloro aromatic ketones was described. Both electron-withdrawing and electron-donating groups on the aromatic rings are well tolerated under the optimized conditions. The 2-chloro aromatic ketones obtained by our method could be applied to synthesize the derivatives of 1H-indazole or benzo[d]isoxazole.     

When C–H bond functionalization meets visible-light photoredox catalysis

In recent years, visible-light-mediated C–H bond functionalization has become an emerging field at the forefront of organic synthesis. It is of considerable interest to academic and industrial chemists owing to the atom/step economical features as well as the overall sustainability. In this Letter, we mainly discussed the recent typical examples in sp² and sp³ C–H bond functionalization by means of visible-light photoredox catalysis.     

Selective C–H bond functionalization with light-driven P450 biocatalysts

The unique photochemical properties of Ru(II)-diimine photosensitizers have enabled light-induced electron transfers in hybrid P450 heme domain enzymes. Rapid quenching of the excited state by soluble molecules generates either a highly oxidative or reductive species depending on the nature of the quencher. Under flash quench oxidative conditions, the heme cofactor of the P450 BM3 enzyme is oxidized to a high-valent ferryl species. Meanwhile, a photogenerated reductive species is able to deliver the necessary electrons to P450 heme active sites and sustain photocatalytic activity in the selective hydroxylation of substrate C–H bonds.     

Indium trichloride catalyzed sp C–H bond functionalization of 2-alkyl azaarenes under microwave irradiation

Microwave promoted indium trichloride (10 mol %) catalyzed sp³ C–H bond functionalization of 2-alkyl azaarenes 1 or 4 has been observed to construct C–C bond either with but-2-ene-1,4-diones 2 or (E)-3-(2-oxo-2-phenylethylidene)indolin-2-one (6) giving access to 2-((quinolin-2-yl)methyl)butane-1,4-diones 3, 2-((pyridin-2-yl)methyl)butane-1,4-diones 5, or 3-(quinolin-2-yl)propan-2-yl)indolin-2-ones 7 in good yields using 1,4-dioxane as solvent.     

Facile cleavage of C–C bond: conversion of pyrane derivative to 1,3-oxazin derivative

A cascade reaction that involves a unique C–C bond cleavage has been discovered. This protocol affords an unusual and facile method for the synthesis of 1,3-oxazin derivatives under mild conditions.     

Mini-review on the functionalization of C–H bond to C-X linkage via metalla-electrocatalyzed tool

To date, the C–H activation protocol and its functionalization of bonds via transition metal have witnessed major attention in coordination chemistry as they eliminate the pre-functionalization of the substrate. Conventional approaches use a stoichiometric amount of chemical oxidants which are toxic under mild conditions. This will create a major problem in C–H functionalization reactions that involve a selective issue of reductive elimination from metal center to form a significant amount of by-product (waste) in large amount which is difficult to separate and thus reduce atom economy and sustainability of the reaction medium. This will limit catalyst turnover and thus, decreases the reaction rate. To avoid this, there is an urgent need for renewable resources which bring about the functionalization of the C–H bond. Metalla-electro catalyzed is the cleanest tool on the platform of C–H activation chemistry. Here, electricity was being involved as a clean surrogate of chemical oxidant and holds unleashed potential for an oxidative protocol of C–H activation with unmet site selectivity. This mini-review pay attention to the C–H functionalization of the bond to C–C, C–N, and C-Miscellaneous (P, O, and S) bond linkage by employing different transition metal {precious (Pd, Rh, Ru, and Ir)} and {earth-abundant (Mn, Ni, Co, and Cu)} using the electrochemical tool. Such metalla-electro catalyzed tools are helpful to those who were not being trained electrochemists but can unleash this potential benefit in various sustainable organic transformations.     

Pd-catalysed intramolecular regioselective arylation of 2-pyrones,pyridones, coumarins and quinolones by C–H bond functionalization

The intramolecular arylation of 2-pyrones, 2-pyridones, coumarins and quinolones is reported using Pd^II precatalyst sources without added phosphine ligands. The excellent yields and convenient reagents enables the formation of various analogues containing these moieties, and access to potential biologically active candidates. Stoichiometric studies were carried out to provide an insight into the oxidation addition step. A switch in regioselectivity, together with a hydrodebromination process, was observed in the case of a 3-bromo-2-pyrone.     

Carbon–hydrogen (C–H) bond activation at PdIV: a Frontier in C–H functionalization catalysis

The direct functionalization of carbon–hydrogen (C–H) bonds has emerged as a versatile strategy for the synthesis and derivatization of organic molecules. Among the methods for C–H bond activation, catalytic processes that utilize a Pd^II/Pd^IV redox cycle are increasingly common. The C–H activation step in most of these catalytic cycles is thought to occur at a Pd^II centre. However, a number of recent reports have suggested the feasibility of C–H cleavage occurring at Pd^IV complexes. Importantly, these latter processes often result in complementary reactivity and selectivity relative to analogous transformations at Pd^II. This mini review highlights proposed examples of C–H activation at Pd^IV centres. Applications of this transformation in catalysis as well as mechanistic details obtained from stoichiometric model studies are discussed. Furthermore, challenges and future perspectives for the field are reviewed.     

Silver-mediated C–H bond functionalization: one-pot to construct substituted indolizines from 2-alkylazaarenes with alkynes

A new silver-mediated highly selective C–H functionalization of 2-alkylazaarenes with internal and terminal alkynes for the creation of substituted indolizines in one-pot has been demonstrated. This process firstly represents a simple, efficient, and atom-economic way to construct polysubstituted indolizines in good yields from internal and terminal alkynes through C–H functionalization of 2-alkylazaarenes.     

Challenges in C–C bond formation through direct transformations of sp2 C–H bonds

In the past several decades, organic chemists have made significant contributions to approach direct C–H transformations. However, limited substrate scope and reaction classifications, harsh condition, and the use of noble and toxic late transition-metal catalysts typically with high loadings clogged its applications. This article summarizes our recent efforts to explore new reaction types and develop new catalytic systems in this field, which may open a new channel to consider organic synthesis from easily available chemicals.     

Toward the most versatile fluorophore: Direct functionalization of BODIPY dyes via regioselective C–H bond activation

Fluorescent dyes are heavily sought for their potentials applications in bioimaging, sensing, theranostic,and optoelectronic materials. Among them, BODIPY dyes are privileged fluorophores that are now widely used in highly diverse research fields. The increasing success of BODIPY dyes is closely associated with their excellent and tunable photophysical properties due to their rich functionalization chemistry.Recently, growing research efforts have been devoted to the direct functionalization of the BODIPY core,because it allows the facile installation of desired functional groups in a single atom economical step. The challenges of this direct C–H derivation come from the difficulties in finding suitable functionalization agents and proper control of the regioselectivity of the functionalization. The aim of this work is to provide an overview of BODIPY dyes and a summarization of the different synthetic methodologies reported for direct C–H functionalization of the BODIPY framework.     

Synthesis of N-benzothiazol-2-yl-amides by Pd-catalyzed C(sp~2)–H functionalization

A catalytic synthesis of N-benzothiazol-2-yl-amides from 1-acyl-3-(phenyl)thioureas was achieved in the presence of a palladium catalyst through the C(sp2)–H functionalization/C–S bond formation. This synthetic methodology can produce various N-benzothiazol-2-yl-amides in high yields with good functional group tolerance.     

Transformations of N-arylpropiolamides to indoline-2,3-diones and acids via C≡C triple bond oxidative cleavage and C(sp^2)–H functionalization

A new palladium-catalyzed oxidative conversion of N-arylpropiolamides and H2O to various indoline-2,3-diones and acids through the C≡C triple bond cleavage and C(sp2)–H functionalization is described,which is promoted by a cooperative action of catalytic CuBr2,2,2,6,6-tetramethyl-1-piperidinyloxy(TEMPO)and O2.The method provides a practical tool for transformations of alkynes by means of a C–H functionalization strategy,which enables the formation of one C–C bond and multiple C–O bonds in a single reaction with high substrates compatibility and excellent functional group tolerance.     

Recent advances in mechanochemical C–H functionalization reactions

The mechanochemical synthesis has provided a greener alternative to solution-based approaches by eliminating the use of organic solvents and reducing the energy consumption. The C–H functionalization is among the most concise and economical synthetic strategies. The combination of the benefits from these two methods provides new opportunities to further increase the efficiency and sustainability of organic synthesis. In this digest, we aim to provide a brief overview of the recent advances in mechanochemical C–H functionalization reactions.     

Iron-mediated remote C–H bond benzylation of 8-aminoquinoline amides

An efficient and convenient method for C5-benzylation of quinoline frameworks is developed with the using of inexpensive FeCl₃ catalyst. A range of N-bisbenzylic and N-monobenzylic sulfonamides smoothly react with aliphatic amides and aromatic amides, giving the corresponding products in moderate to excellent yields.     

Silver-catalyzed decarboxylative C–H functionalization of cyclic aldimines with aliphatic carboxylic acids

Silver-catalyzed decarboxylative C–H alkylation of cyclic aldimines with abundant aliphatic carboxylic acids has been realized under mild reaction conditions generating the corresponding products in moderate to good yields (32%–91%). In addition, a gram-scale reaction, late-stage modification of drug, synthetic transformation of the product, and further application of the catalytic strategy were also performed. Preliminary studies indicate that the reaction undergoes a radical process.     

Nano CuO-catalyzed C–H functionalization of 1,3-azoles with bromoarenes and bromoalkenes

Copper oxide catalyzed direct C–H arylation and alkenylation of aromatic heterocycles using aryl and alkenyl bromides have been developed and have been applied to the C–H functionalization of a variety of 1,3-azoles like benzoxazole, benzothiazole, 1-methylbenzimidazole, and 1-methylimidazole, with moderate to excellent yields. The best performance has been achieved in the presence of PPh₃ when average size of CuO nanoparticles is 6.5 nm. This catalyst can be recovered and reused without significant decrease in its catalytic activity.     

CH bond functionalization: emerging synthetic tools for natural products and pharmaceuticals

The direct functionalization of C? H bonds in organic compounds has recently emerged as a powerful and ideal method for the formation of carbon–carbon and carbon–heteroatom bonds. This Review provides an overview of C? H bond functionalization strategies for the rapid synthesis of biologically active compounds such as natural products and pharmaceutical targets.     

C–H bond activation in the total syntheses of natural products

The transition metal-mediated C–H bond activation has emerged as a powerful and ideal method for the total syntheses of natural products and pharmaceuticals, and has had a significant impact on synthetic planning and strategy in complex natural products.In this review, we describe selected recent examples of the transition metal-mediated C–H bond activation strategies for the rapid syntheses of natural products.