Mechanochemical Transformation of CF 3 Group: Synthesis of Amides and Schiff Bases

Ruthenium Catalyzed Mechanochemical Transformation of Sulfonamide Group to Fluoro, Trifluoromethyl, and Trifluoromethoxy Functionalities

A convenient route for the mechanochemical synthesis of fluorinated aromatic compounds, that is, fluoro, trifluoromethyl, and trifluoromethoxy arenes, has been developed via pyrylium tetrafluoroborate (Pyry-BF4)-mediated desulfonamidative cross-coupling of primary sulfonamides under the synergy of a piezoelectric material BaTiO3, and Ru-catalysis. This is the first-ever report on the selective transformation of sulfonamide (SO2NH2) functionality to CF3/OCF3/F group in a single step under mechanochemical ball-milling conditions. Considering the importance of primary sulfonamides as the valuable pharmacophores, the present desulfonamidative cross-coupling approach could have potential to get synthetic utility in pharmaceutical industries for the late-stage functionalization of sulfonamide drugs and related active pharmaceutical ingredients (APIs).

Organotin(IV) derivatives of 4-chloro-2-methylphenoxyacetic acid: synthesis, spectral characterization, X-ray structures, anticancer, enzyme inhibition, antileishmanial, antimicrobial and antioxidant activities

Four organotin(IV) carboxylate complexes; (C4H9)3SnL (1), CH3SnL (2), (C4H9)2SnL2 (3) and (CH3)2SnL2 (4) are synthesized by the condensation reaction of organotin(IV) chlorides with sodium-4-chloro-2-methylphenoxyacetate (NaL). The FT-IR spectra suggested bridging/chelating bidentate coordination of the ligand to the tin atom. Single-crystal XRD analysis authenticated the FT-IR findings for 1 and 2. The NMR study has shown no significant differences in the signals of the free and coordinated ligand except for absence of a proton and up-filed/down-field shift of the C signal of the carboxyl group in the spectra. Complexes 1-4 have shown better enzyme inhibition, antioxidant, antimicrobial, and anticancer activities compared to the free ligand acid. Complex 3 was the most active inhibitor of AChE, BChE, α-glucosidase and α-amylase with IC50 values of 43.76, 102.39, 232.71 and 91.84 µg/mL, respectively. Additionally, 3 with IC50 values of 7.52 and 8.77 µg/mL in the DPPH and ABTS assays, respectively was better antioxidant than the standard. Complex 4 was the most efficient inhibitor of MAO-B and COX-2 enzymes with IC50 values of 106.99 and 12.98 µg/mL, respectively, while 1 (IC50 = 38.97 µg/mL) has shown the highest 5-LOX inhibition potential. Complexes 1-4 with IC50 values in the range 237.51-168.35 µg/mL have shown better antileishmanial activity than HL (IC50 = 277.57 µg/mL). The compounds showed good to potent antiproliferative activity in malignant glioma U87 cells with IC50 values in the range 12.54 ± 0.05 to 37.65 ± 0.04 µg/mL. Antimicrobial activities have shown promising results for the compounds compared to the standards in some cases.

Reusable Iron-Copper Catalyzed Cross-Coupling of Primary Amides with Aryl and Alkyl Halides: Access to N-Arylamides as Potential Antibacterial and Anticancer Agents

We present, for the first time, an efficient ligand-free iron-copper catalyzed cross-coupling reaction involving a variety of aryl, heteroaryl halides (including chlorides, bromides, and iodides), and alkyl bromides with diverse aryl and aliphatic primary amides, conducted under solvent-minimized conditions. This economically competitive protocol successfully yielded the corresponding cross-coupling products, N-arylamides and N-alkylamides, in good to excellent yields with broad substrate scope (65 examples) and tolerance to several sensitive functionalities (including heterocycles). No conventional work-up is required for this protocol, and the developed method is applicable for gram-scale synthesis. Notably, the catalyst is inexpensive, environmentally friendly, and can be reused at least four times with minimal loss of catalytic activity. A series of experiments, including X-ray photoelectron spectroscopy (XPS), UV spectroscopy, cyclic voltammetry (CV), electron paramagnetic resonance (EPR), and X-ray diffraction (XRD) were conducted to identify the oxidation state of active catalytic species and radical clock experiment was performed using a radical probe to investigate the reaction mechanism. Furthermore, we evaluated the antibacterial and anticancer properties of selected synthesized products (3 ii, 3 xii, and 3 xxxx) in-vitro. The results indicated that the prepared compounds exhibited promising antibacterial and anticancer activities (MTT and Molecular Docking).

Ru-catalyzed activation of free phenols in a one-step Suzuki-Miyaura cross-coupling under mechanochemical conditions

Activation of phenols by a Ru-catalyst allows for the resulting η5-phenoxo complex to selectively react with a variety of nucleophiles under mechanochemical conditions. Conversion of phenolic hydroxy groups without derivatization is important for late-stage modifications of pharmaceuticals and in the context of lignin-material processing. We present a one-step, Ru-catalyzed cross-coupling of phenols with boronic acids, aryl trialkoxysilanes and potassium benzoyltrifluoroborates under mechano-chemical conditions. The protocol accepts a wide scope of starting materials and allows for gram-scale synthesis in excellent yields. The developed approach constitutes a very interesting and waste-limiting alternative to the known methods.

Simplified Version of the Eschweiler-Clarke Reaction

The traditional Eschweiler-Clarke reaction is a three-component process involving formaldehyde, amine, and formic acid. In this work, we showed that the reductive potential of formaldehyde was sufficient to provide methylation of secondary amines in the absence of acidic additives. Various acid-sensitive moieties remain intact under developed conditions. The scalability of the elaborated approach was shown for several products. Synthesis of the antifungal agent butenafine demonstrated the preparative utility of the developed approach.

Photoinduced copper-catalyzed C-N coupling with trifluoromethylated arenes

Selective defluorinative functionalization of trifluoromethyl group (-CF3) is an attractive synthetic route to the pharmaceutically privileged fluorine-containing moiety. Herein, we report a strategy based on photoexcited copper catalysis to activate the C-F bond of di- or trifluoromethylated arenes for divergent radical C-N coupling with carbazoles and aromatic amines. The use of different ligands can tune the reaction products diversity. A range of substituted, structurally diverse α,α-difluoromethylamines can be obtained from trifluoromethylated arenes via defluorinative C-N coupling with carbazoles, while an interesting double defluorinative C-N coupling is ready for difluoromethylated arenes. Based on this success, a carbazole-centered PNP ligand is designed to be an optimal ligand, enabling a copper-catalyzed C-N coupling for the construction of imidoyl fluorides from aromatic amines through double C-F bond functionalization. Interestingly, a 1,2-difluoroalkylamination strategy of styrenes is also developed, delivering γ,γ-difluoroalkylamines, a bioisostere to β-aminoketones, in synthetically useful yields. The DFT studies reveal an inner-sphere electron transfer mechanism for Cu-catalyzed selective activation of C(sp3)-F bonds.

C-F Transformations of Benzotrifluorides by the Activation of Ortho-Hydrosilyl Group

Single C-F transformations of aromatic trifluoromethyl compounds are challenging issues due to the strong C-F bond. We have recently developed selective methods for single C-F transformations such as allylation of o-hydrosilyl-substituted benzotrifluorides through the hydride abstraction with trityl cations. Single C-F thiolation and azidation of o-(hydrosilyl)benzotrifluorides were achieved using trityl sulfides and trityl azide catalyzed by Yb(OTf)3 . Treatment of o-(hydrosilyl)benzotrifluorides with trityl chloride resulted in single C-F chlorination. The resulting fluorosilyl group served in further transformations including protonation, halogenation, and Hiyama cross-coupling with C-Si cleavage. We also synthesized benzyl fluorides by LiAlH4 -reduction of the resulting fluorosilanes and further C-F transformations. These methods enabled us to prepare a broad range of organofluorines from simple benzotrifluorides through C-F and C-Si transformations.

Mechanochemical arylative detrifluoromethylation of trifluoromethylarenes

The stoichiometric defluorinative functionalization of ArCF3 is a conceptually appealing research target. It enables the challenging late-stage functionalization of CF3-containing aromatic molecules and contributes to the remedy of environmental risks resulting from the accumulation of relatively inert ArCF3-containing molecules. Similarly, Ar-CN bond features limit their utilization in cross-coupling reactions. Thus, the employment of benzonitriles in decyanative Suzuki-Miyaura type coupling remains in high demand in the field of C-C bond formation. Herein, we report mechanochemically induced and ytterbium oxide (Yb2O3)-mediated defluorinative cyanation of trifluoromethylarenes. In addition, we describe a facile mechanochemically facilitated and nickel-catalyzed decyanative arylation of benzonitriles to access biphenyls. Combining both processes in a one-pot multicomponent protocol to achieve a concise direct arylative detrifluoromethylation of ArCF3 is described herein. This work is the first hitherto realization of C-C coupling with CF3 as a formal leaving group.

Mechanochemical Defluorinative Arylation of Trifluoroacetamides: An Entry to Aromatic Amides

The amide bond is prominent in natural and synthetic organic molecules endowed with activity in various fields. Among a wide array of amide synthetic methods, substitution on a pre-existing (O)C-N moiety is an underexplored strategy for the synthesis of amides. In this work, we disclose a new protocol for the defluorinative arylation of aliphatic and aromatic trifluoroacetamides yielding aromatic amides. The mechanochemically induced reaction of either arylboronic acids, trimethoxyphenylsilanes, diaryliodonium salts, or dimethyl(phenyl)sulfonium salts with trifluoroacetamides affords substituted aromatic amides in good to excellent yields. These nickel-catalyzed reactions are enabled by C-CF₃ bond activation using Dy₂O₃ as an additive. The current protocol provides versatile and scalable routes for accessing a wide variety of substituted aromatic amides. Moreover, the protocol described in this work overcomes the drawbacks and limitations in the previously reported methods.

Hydride reduction of o-(fluorosilyl)benzodifluorides for subsequent C–F transformations

An efficient method for sequential C–F transformations of o-hydrosilyl-substituted benzotrifluorides is disclosed. A key to the success is hydride reduction of o-fluorosilyl-substituted difluoromethylenes prepared by a single C–F transformation of...