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Direct C–H amination methods are essential because of the importance of aryl amine derivatives.

A practical method to synthesize quinoxalinones via intra/intermolecular amination using rhodium as the catalyst was developed. A wide variety of quinoxalinones were prepared from N-methoxybenzamides in moderate to excellent yields. Gram-scale reactions were also achieved, highlighting the synthetic importance of this new transformation.

Here, a rhodium(III)-catalyzed benzo[c]azepine-1,3(2H)-dione synthesis via tandem C–H alkylation and intramolecular amination of N-methoxylbenzamide with 3-bromo-3,3-difluoropropene as the alkylation agent is reported. The substituted benzamides and protected indoles are all tolerated, yielding the corresponding products in moderate to good yields. Further study revealed those bioactive compounds such as piperic acid and a key precursor of Roflumilast all perform well, highlighting the synthetic utility of this method.

1,10-Phenanthroline-assisted, Ni(ii)-catalyzed para-carboxylation of phenol derivatives is reported.

A metal-free method for the construction of 3,3-dimethyl isoindolinones via radical-mediated intramolecular coupling of two C–H bonds of N,N-diisopropyl benzamides was developed. The reactions can proceed in moderate to high yield and with excellent chemoselectivity. A reaction sequence of the formation of an alkyl radical via oxidative cleavage of alkyl C–H bond and the formation of lactam ring via intramolecular homolytic aromatic substitution was proposed.

Iodine(III)-mediated synthesis of 4-iodo-N-phenylaniline from iodobenzene has been achieved, and the reaction can proceed under mild conditions. A variety of functional groups were well tolerated, providing the corresponding products in moderate to good yields. The remaining iodine group provides an effective platform for converting the products into several valuable asymmetric diphenylamines. Most importantly, this reaction can be easily scaled up to the ten-gram scale, highlighting its synthetic utility. The mechanistic study revealed that the in situ generated aryl hypervalent iodine intermediate is the key factor to realize this para-selective C-H amination reaction.

Fluorine is well-known as a very special element. Approximately 30% of agrochemicals and 20% of all drugs contain fluorine; most of those compounds have unique functions in biochemistry, pharmacy, and bioscience and those containing alkoxycarbonyldifluoromethyl functional groups often have irreplaceable roles. Therefore, the selective introduction of alkoxycarbonyldifluoromethylated functional groups into various aromatic substrates has significant practical application. This review describes recent advances in selective alkoxycarbonyldifluoromethylation of aromatic substrates by using different catalytic strategies (cyclometalated ruthenium complex, transient regulating and visible-light-induced strategies).1 Introduction2 para-C–H Alkoxycarbonyldifluoromethylation of Aromatic Derivatives2.1 Ruthenium Catalysis2.2 Palladium Catalysis2.3 Visible-Light Catalysis2.4 Iron Catalysis3 meta-C–H Alkoxycarbonyldifluoromethylation of Aromatic Derivatives3.1 Ruthenium Catalysis3.2 Palladium Catalysis4 The Influence of Transition Metals and Directing Groups on Site Selectivity of Alkoxycarbonyldifluoromethylation4.1 The Influence of Directing Groups on the Site Selectivity of Alkoxycarbonyldifluoromethylation4.2 The Influence of Transition Metals on the Site Selectivity of Alkoxycarbonyldifluoromethylation5 Conclusions

A novel approach to synthesize 3-methylisoquinolines via a one-pot, two-step, palladium(II)-catalyzed tandem C-H allylation/intermolecular amination and aromatization is reported. A wide series of 3-methylisoquinoline derivatives were obtained directly using this method in moderate to good yields, and we highlight the synthetic importance of this new transformation.

Direct functionalization of a C-H bond at either the meta or para position by only changing the catalyst system poses a significant challenge. We herein report the [Fe(TPP)Cl]-enabled, selective, C-H difluoromethylation of arenes using BrCF2CO2Et as the difluoromethylation source, which successfully altered the selectivity from the meta to the para position. A preliminary mechanistic study revealed the iron porphyrin complex not only activated the aromatic ring but also induced para selectivity due to the influence of ligand sterics.

With pyrimidine as the directing group, we achieved the meta-selective difluoromethylation of phenol derivatives using ruthenium as a catalyst. This synthetic scheme provided an efficient method for the syntheses of fluorine-containing phenol derivatives. A wide variety of phenol derivatives were well-suited, affording the corresponding products in moderate-to-good yields.

The Bi(OTf)

It has always been a challenge in free radical chemistry to control site selectivity during the reaction of free radicals with aromatic rings. Herein, we report the site-selective carboxylation of anisoles through the direct reaction of the bromoform radical with a benzene ring at the

Visible-light-induced, iridium catalyzed

Palladium-catalyzed non-directed C-H functionalization provides an efficient approach for direct functionalization of arenes, but it usually suffers from poor site selectivity, limiting its wide application. Herein, it is reported for the first time that the proton shuttle of 3,5-dimethyladamantane-1-carboxylic acid (1-DMAdCO2H) can affect the site selectivity during the C-H activation step in palladium-catalyzed non-directed C-H functionalization, leading to highly para-selective C-H olefination of TIPS-protected phenols. This transformation displayed good generality in realizing various other para-selective C-H functionalization reactions such as hydroxylation, halogenation, and allylation reactions. A wide variety of phenol derivatives including bioactive molecules of triclosan, thymol, and propofol, were compatible substrates, leading to the corresponding para-selective products in moderate to good yields. A preliminary mechanism study revealed that the spatial repulsion factor between proton shuttle and bulky protecting group resulted in the selective C-H activation at the less sterically hindered para-position. This new model non-directed para-selective C-H functionalization can provide a straightforward route for remote site-selective C-H activations.

A direct, para-selective, radical-based alkylation of aromatic ketones with alkanes has been developed using a nickel catalyst with oxamide as the ligand. Acetophenones bearing electron-withdrawing substituents were functionalized directly with simple alkanes with high para-selectivity while acetophenones with electron-donating groups were mainly para-functionalized. A mechanistic study indicated that C-H bond activation of the aromatic ring may be the rate-determining step of the reaction.

We report the para-selective C–H benzylation of phenyl carbamate with an iron(II) catalyst. This new method provides an efficient and convenient approach for the synthesis of triarylmethanes starting from readily available anilines and diphenylmethane. Preliminary mechanistic studies revealed that the iron(II) catalyst was essential and the use of the sterically demanding isobutoxy group led to high para-selectivity.

A convenient approach to synthesize o-hydroxybenzylamine via Pd-catalyzed hydroxylation of benzylamine with a removable Cbz-amide as the directing group was developed. Various functional groups were well tolerated, leading to various substituted o-hydroxybenzylamines in moderate to good yields.

A regioselective rhodium-catalyzed carboxylate-directed thiolation process was developed. Several benzoic-acid derivatives and disulfides were found to be well-tolerated, and they yielded the corresponding products in moderate to good yields. Compounds such as the key precursor of roflumilast can be obtained via this reaction, thereby highlighting the potential of this synthetic approach.

The development of new methods to achieve the direct synthesis of bioactive organic molecules is always an important topic in organic synthesis. We hereby demonstrate that N-methoxyamide is an exce...

Highly efficient alkylation of β-chloro ketones and their derivatives was achieved by means of domino dehydrochlorination/Mn-enabled radical-based alkyl-alkyl cross-coupling reaction. In situ-generated α,β-unsaturated ketones and their analogues were identified as the reaction intermediates. Known bioactive compounds, such as melperone and azaperone, could be easily prepared from β-chloropropiophenone in two steps.

The Rh(III)-catalyzed amidation of C(sp2)–H bonds has been reported by employing the N-methoxyamide as a novel amino source. An excellent level of functional group tolerance can be achieved when N-methoxyamide derivatives are used as the amidating reagents. Importantly, several known bioactive compounds such as Aminalon, Pregabalin, Gabapentin, and Probenecid can be transformed to effective amidating reagents, as a way to facilitate the development of new bioactive molecules.

A palladium-catalyzed carboxylic acid-directed cross-coupling of an ortho-C(sp2) atom of aromatic acids with aliphatic aziridines to construct the β-arylethylamine skeleton via C–H activation has been developed. The reaction proceeded under mild conditions with great substrate scope. Meanwhile, the β-arylethylamine skeleton in drugs or bioactive compounds could be easily generated in a single step. A catalytic amount of cesium carbonate was crucial to realizing the selective β-arylethylamine synthesis.

The direct incorporation of a trifluoromethyl group on an aromatic ring using a radical pathway has been extensively investigated. However, the direct highly para-selective C-H trifluoromethylation of a class of arenes has not been achieved. In this study, we report a light-promoted 4,5-dichlorofluorescein (DCFS)-enabled para-selective C-H trifluoromethylation of arylcarbamates using Langlois reagent. The preliminary mechanistic study revealed that the activated organic photocatalyst coordinated with the arylcarbamate led to para-selective C-H trifluoromethylation. Ten-gram scale reaction performs well highlighting the synthetic importance of this new protocol.

Iodine(III)-mediated synthesis of 4-iodo

We report a palladium-catalyzed, ligand promoted, C-H fluorine-containing olefination of anilides with 4-bromo-3,3,4,4-tetrafluorobutene as the fluorinated reagent, which has a potential transformation into other compounds due to its -CF2CF2Br functional group. -CF2CF2H was obtained by using the mild reducing agent sodium borohydride. Bioactive compounds such as aminoglutethimide derivative and propham were well-tolerated in this reaction, both of which highlight the synthetic importance of this method.

A novel Cu(CH3CN)4PF6-catalyzed carboamination reaction of 8-aminoquinoline-oriented buteneamides with chloroform to afford 4-(2,2,2-trichloroethyl)-β-lactams is described. The reaction proceeded at 110 °C in air with di-t-butyl peroxide. Preliminary studies indicated that the reaction undergoes a free radical mechanism via a Cu(I)/Cu(II)/Cu(III) catalytic cycle.

We report herein a direct method to synthesize 4-aryl-3-butenoic acid through a carboxylic-acid-directed oxidative Heck reaction. The various 4-aryl-3-butenoic acids are easily prepared in moderate to good yields. In view of the promising bioactivity of 4-phenyl-3-butenoic acid previously reported, its derivatives reported here may be bioactive.

Highly efficient, palladium-catalyzed, para-selective difluoromethylation of arene esters has been developed using [1,1'-biphenyl]-2-dicyclohexylphosphine as the effective ligand. A wide variety of arene esters bearing various functional groups were all compatible with the reaction conditions, leading to para-difluoromethylated products in moderate to good yields. Moreover, benzoylamide and benzenesulfonamide were also well-tolerated, suggesting that this novel catalyst system has broad applications to a variety of substrates.

3-Bromo-1,1,1-trifluoroacetone was first disclosed as an effective indirect trifluoromethylation reagent to construct the important 3-trifluoromethyl isocoumarin skeleton. The reaction proceeds through a ligand-promoted, iridium-catalyzed ortho-selective C-H alkylation of benzoic acid and an intermolecular cyclization reaction promoted by silver acetate. A wide range of 3-trifluoromethyl isocoumarins can be easily obtained in moderate to good yields. Importantly, the isocoumarin skeleton can be easily formed in bioactive compounds, highlighting the importance of this reaction.

A highly efficient silver-catalyzed dibenzylation of acetanilides by employing the benzhydrol derivatives as the coupling partners to yield triphenylmethane derivatives has been developed. Various functional groups were tolerated, leading to the corresponding products in moderate to good yields. Preliminary experimental results indicated that the silver ions activate the arene rings and the strong acid TfOH provides the carbocations.

An efficient synthesis of isoindolin-1-ones from oxalyl amide-protected benzylamines, through ruthenium-catalyzed intramolecular C(sp2)-H carbonylation, has been developed. Variously substituted benzylamines could be well tolerated in this new protocol, affording the corresponding products in moderate to excellent yields. This approach constitutes the first example of Ru(II)-catalyzed C(sp2)-H carbonylation with isocyanate as a novel commercially available carbonyl source.