Synthesis of Benzidine Derivatives via FeCl3·6H2O-Promoted Oxidative Coupling of Anilines

H2 O ⋅ B(C6 F5 )3 -Catalyzed para-Alkylation of Anilines with Alkenes Applied to Late-Stage Functionalization of Non-Steroidal Anti-Inflammatory Drugs

Anilines are core motifs in a variety of important molecules including medicines, materials and agrochemicals. We report a straightforward procedure that allows access to new chemical space of anilines via their para-C-H alkylation. The method utilizes commercially available catalytic H2 O ⋅ B(C6 F5 )3 and is highly selective for para-C-alkylation (over N-alkylation and ortho-C-alkylation) of anilines, with a wide scope in both the aniline substrates and alkene coupling partners. Readily available alkenes are used, and include new classes of alkene for the first time. The mild reaction conditions have allowed the procedure to be applied to the late-stage-functionalization of non-steroidal anti-inflammatory drugs (NSAIDs), including fenamic acids and diclofenac. The formed novel NSAID derivatives display improved anti-inflammatory properties over the parent NSAID structure.

Metal-free photoredox-catalyzed direct α-oxygenation of N,N-dibenzylanilines to imides under visible light

An efficient synthesis of imides using metal-free photoredox-catalyzed direct α-oxygenation of N,N'-disubstituted anilines in the presence of 9-mesityl-10-methylacridinium [Acr+-Mes]BF4 as a photoredox catalyst and molecular oxygen as a green oxidant under visible light was developed. This photochemical approach offered operational simplicity, high atom economy with a low E-factor, and functional group tolerance under mild reaction conditions. Control and quenching experiments confirmed the occurrence of a radical pathway and superoxide radical anion α-oxygenation reactions, and also provided strong evidence for the reductive quenching of [Acr+-Mes]BF4 based on a Stern-Volmer plot, which led to the proposed mechanism of this reaction.

Regioselective Synthesis of 2° Amides Using Visible-Light-Induced Photoredox-Catalyzed Nonaqueous Oxidative C-N Cleavage of N,N-Dibenzylanilines

A visible-light-driven photoredox-catalyzed nonaqueous oxidative C-N cleavage of N,N-dibenzylanilines to 2° amides is reported. Further, we have applied this protocol on 2-(dibenzylamino)benzamide to afford quinazolinones with (NH₄)₂S₂O₈ as an additive. Mechanistic studies imply that the reaction might undergo in situ generation of α-amino radical to imine by C-N bond cleavage followed by the addition of superoxide ion to form amides.

Reductive Alkylation of Quinolines to N-Alkyl Tetrahydroquinolines Catalyzed by Arylboronic Acid

A boronic acid catalyzed one-pot tandem reduction of quinolines to tetrahydroquinolines followed by reductive alkylation by the aldehyde has been demonstrated. This step-economcial synthesis of N-alkyl tetrahydroquinolines has been achieved directly from readily available quinolines, aldehydes, and Hantzsch ester under mild reaction conditions. The mechanistic study demonstrates the unique behavior of organoboron catalysts as both Lewis acids and hydrogen-bond donors.

Electro-oxidative C(sp2)–H/O–H cross-dehydrogenative coupling of phenols and tertiary anilines for diaryl ether formation

The selective electrochemical oxidation of tertiary anilines in the presence of phenolic reactants leads to diaryl ether products.

Catalytic and Aerobic Oxidative Biaryl Coupling of Anilines Using a Recyclable Heterogeneous Catalyst for Synthesis of Benzidines and Bicarbazoles

In this study, a heterogeneous rhodium-catalyzed oxidative homocoupling reaction of anilines utilizing molecular oxygen as the sole oxidant is reported. Employing a commercially available and recyclable Rh/C catalyst enabled the oxidative dimerization of various anilines, including N,N-disubstituted and N-monosubstituted anilines, as well as diarylamines, triarylamines, and carbazoles. Additionally, the catalytic protocol was extended to the ortho-ortho coupling of anilines, affording 2,2'-diaminobiphenyls with high regioselectivity. Notably, the developed approach provides rapid access to diversely functionalized benzidines and diaminobiphenyls in an operationally simple, practical, and environmentally friendly manner.

Highly Selective Synthesis of Hydrazoarenes from Nitroarenes via Polystyrene-Supported Au-Nanoparticle-Catalyzed Reduction: Application to Azoarenes, Aminoarenes, and 4,4'-Diaminobiaryls

A selective synthesis of hydrazoarene from nitroarene and its application are reported. Using polystyrene (PS) resins as solid supports for Au nanoparticles (AuNPs), polystyrene-supported Au nanoparticles (AuNPs@PS) were synthesized and characterized. In the presence of AuNPs@PS (1.0 mol %) as a catalyst, nitroarenes afforded corresponding hydrazoarenes (up to 99%) with high selectivity (up to 100%) under mild reaction conditions (NaBH₄, 50% aq. EtOH, and room temperature). Depending on the reaction conditions (the amount of NaBH₄, the substituent of nitroarenes, and the sequential addition of HCl), nitroarenes were converted to corresponding azoarenes (up to 95%), aminoarenes (up to 99%), and 4,4'-diaminobiaryls (up to 99%). Our easily recyclable catalytic system using a solid-phase reaction vessel provides an attractive synthetic method in an eco-friendly and sustainable manner.

Iron-Catalyzed Oxidative C-C Cross-Coupling Reaction of Tertiary Anilines with Hydroxyarenes by Using Air as Sole Oxidant

A mild procedure for the oxidative C-C cross-coupling of tertiary anilines with phenols is described which provides the products generally in high yields and with excellent selectivity. The reaction is catalyzed by the hexadecafluorinated iron-phthalocyanine complex FePcF16 in the presence of substoichiometric amounts of methanesulfonic acid and ambient air as sole oxidant.

Absolute Configuration Assignment from Optical Rotation Data by Means of Biphenyl Chiroptical Probes

A non-empirical approach for the assignment of the absolute configuration of chiral 2-alkyl-substituted carboxylic acids and primary amines by [α]_D measurements has been developed. The method requires the conversion of the chiral acids or amines into the corresponding 4,4'-disubstituted biphenylamides or biphenylazepines, respectively. In these derivatives a central-to-axial chirality transfer induces a preferred torsion in the biphenyl moiety revealed by the sign of the biphenyl A band in the ECD spectrum. By 4,4'-substitution on the biphenyl moiety a redshift of the A band is obtained, leading to an increase of its relative contribution to optical rotation. This allows to reliably establish a direct correlation between the [α]_D sign, the biphenyl twist and, then, the substrate absolute configuration. This approach thus constitutes a really practical and reliable method to assign the absolute configuration of chiral carboxylic acids and primary amines by simple and straightforward [α]_D measurement, readily obtainable by a routine instrumentation like the polarimeter.

A metal- and oxidizing-reagent-free anodic para-selective amination of anilines with phenothiazines

A highly para-selective amination of anilines with phenothiazines for producing various functionalized 10-aryl-10H-phenothiazines is reported.

Alkylarylation of styrenes via direct C(sp3)–Br/C(sp2)–H functionalization mediated by photoredox and copper cooperative catalysis

For straightforward access to various substituted 1,1-diarylalkanes a photoredox-catalyzed and copper-promoted 1,2-alkylarylation reaction of styrenes has been developed, which uses α-carbonyl alkyl bromides and N,N-disubstituted anilines as functionalization reagents.

Deuterodechlorination of Aryl/Heteroaryl Chlorides Catalyzed by a Palladium/Unsymmetrical NHC System

The catalytic deuterodechlorination of aryl/heteroaryl chlorides was developed with a palladium/unsymmetrical NHC system, and the precisely controlled introduction of deuterium into a variety of aryl/heteroaryl compounds was achieved with a high level of efficiency, selectivity, and deuteration degree. This method was also successfully applied to the transformation of bioactive agents even in a gram-scale synthesis. The crystal structure analysis of Pd-NHC complexes led to the observation of Pd-arene interaction.

Iron-catalysed sequential reaction towards α-aminonitriles from secondary amines, primary alcohols and trimethylsilyl cyanide

We have developed a one-pot iron-catalysed sequential reaction of secondary amines with primary alcohols, trimethylsilyl cyanide and TBHP under mild reaction conditions to give the corresponding α-aminonitriles.

5-Position-selective C–H trifluoromethylation of 8-aminoquinoline derivatives

A rare example of C–H trifluoromethylation at the remote position of 8-aminoquinoline derivatives was realized by using a CuCl catalyst/Togni's reagent system.

A concise synthesis of quinolinium, and biquinolinium salts and biquinolines from benzylic azides and alkenes promoted by copper(ii) species

​A copper promoted multiple aza-[4 + 2] cycloaddition reactions between benzylic azides and alkenes to form four different products including quinolinium and biquinolinium cations, biquinolines and quinolines are described.

A biphenyl containing two electron-donating and two electron-accepting moieties: a rigid and small donor–acceptor–donor ladder system

A small ladder-type donor–acceptor–donor π-system, a biphenyl furnishing two phosphine oxide bridges and two amino groups, showed significantly red-shifted absorption and fluorescence.

Unexpected CN bond formation via NaI-catalyzed oxidative de-tetra-hydrogenative cross-couplings between N,N-dimethyl aniline and sulfamides

A direct de-tetra-hydrogenative cross-coupling reaction between C_sp3–H bonds and sulfamide under transition-metal-free conditions is reported to give the corresponding amidines.