Multiple biological active 4-aminopyrazoles containing trifluoromethyl and their 4-nitroso-precursors: Synthesis and evaluation

4-Nitroso-3-trifluoromethyl-5-alkyl[(het)aryl]pyrazoles were synthesized via one-pot nitrosation of 1,3-diketones or their lithium salts followed by treatment of hydrazines. Reduction of nitroso-derivatives made it possible to obtain 4-amino-3-trifluoromethylpyrazoles chlorides. According to computer-aided calculations, all synthesized compounds are expected to have acceptable ADME profile for drug design. Tuberculostatic, antibacterial, antimycotic, antioxidant and cytotoxic activities of the compounds were evaluated in vitro, while their analgesic and anti-inflammatory action was tested in vivo along with acute toxicity studies. N-Unsubstituted 4-nitrosopyrazoles were the most effective tuberculostatics (MIC to 0.36 μg/ml) and antibacterial agents against Streptococcus pyogenes (MIC to 7.8 μg/ml), Staphylococcus aureus,S. aureus MRSA and Neisseria gonorrhoeae (MIC to 15.6 μg/ml). 4-Nitroso-1-methyl-5-phenylpyrazole had the pronounced antimycotic action against a wide range of fungi (Trichophytonrubrum, T. tonsurans, T. violaceum, T. interdigitale, Epidermophytonfloccosum, Microsporumcanis with MIC 0.38-12.5 μg/ml). N-Unsubstituted 4-aminopyrazoles shown high radical-scavenging activity in ABTS test, ORAC/AAPH and oxidative erythrocyte hemolysis assays. 1-Methyl-5-phenyl-3-trifluoromethylpyrazol-4-aminium chloride revealed potential anticancer activity against HeLa cells (SI > 1351). The pronounced analgesic activity was found for 4-nitroso- and 4-aminopyrazoles having phenyl fragment at the position 5 in "hot plate" test. The most of the obtained pyrazoles had a moderate acute toxicity.

Synthesis of Heteroannulated Indolopyrazines through Domino N-H Palladium-Catalyzed/Metal-Free Oxidative C-H Bond Activation

A convenient approach to [1,2,5]oxadiazolo[3',4':5,6]pyrazino[2,3-b]indoles and their heteroannulated analogues bearing various aryl substituents in the backbone has been developed. This synthetic protocol is based on Pd-catalyzed Buchwald-Hartwig and subsequent annulation by intramolecular oxidative cyclodehydrogenation. The photophysical properties for new polycycles have been measured.

Dibenzo[f,h]furazano[3,4-b]quinoxalines: Synthesis by Intramolecular Cyclization through Direct Transition Metal-Free C-H Functionalization and Electrochemical, Photophysical, and Charge Mobility Characterization

Herein, we describe the synthesis of unsymmetrically substituted dibenzo[f,h]furazano[3,4-b]quinoxalines by intramolecular cyclization through direct transition metal-free C-H functionalization. The electrochemical and photophysical properties for several polycycles have been measured. In thin films of the dibenzo[f,h]furazano[3,4-b]quinoxalines, hole mobility is in the order of 10^-4 cm² V^-1 s^-1. The results show that the HOMO and LUMO energy levels are appropriate for using the compounds as hole-transport materials in thin-film devices, in particular, organic and perovskite solar cells.

Synthetic Approaches to Unsymmetrically Substituted 5,7-Dihydroxycoumarins

The chemical equivalence of the hydroxy groups in the 5,7-dihydroxycoumarin core has challenged synthetic chemists to develop short and efficient strategies for the selective modification of one of the hydroxy groups leaving the second intact. Over the past 100 years, chemists have proposed various approaches to distinguishing between these two groups according to their reactivity. While the early syntheses included simple nonselective reactions of both hydroxy groups and the subsequent separation of mixtures of the 5-O- and 7-O-isomers formed, recent sophisticated approaches often include the introduction of protective groups for selective directing reactions or the completely controlled construction of the 5,7-dihydroxycoumarin framework by Horner–Wadsworth–Emmons reaction. This review discusses in detail approaches towards unsymmetrically substituted 5,7-dihydroxycoumarins as well as factors influencing 5-O vs. 7-O regioselectivity of reactions of 5,7-dihydroxycoumarins. This review covers all the literature since 1921 with an emphasis on recent works. This critical review may facilitate the synthesis of new drug candidates as well as the total synthesis of natural products.

1 Introduction

2 O-Modification of 5,7-Dihydroxycoumarins

2.1 Alkylation/Alkenylation

2.2 Acylation

2.3 Sulfonylation

2.4 Silylation

2.5 Acylation Followed by Alkylation

3 Other Approaches

3.1 Synthesis from Substituted Phloroglucinol

3.2 Synthesis from Derivatives of 2-Acylphloroglucinol

4 Conclusion

Recent advances in the synthesis of fluorinated compounds via an aryne intermediate

In this review, the usefulness of aryne intermediates for the synthesis of various fluorinated organic compounds during the last decade has been demonstrated.

Azaheterocyclic Derivatives of ortho-Carborane: Synthetic Strategies and Application Opportunities

Azaheterocyclic derivatives of 1,2-dicarba-closo-dodeca­borane (ortho-carborane) are known to be of particular interest due to numerous plausible applications, particularly, in medicine, materials science, and advanced technologies. Three principal synthetic strategies resulting in azaheterocyclic carboranes, in which boron-enriched and azaheterocyclic fragments are linked to each other, either directly by means of the C–C bonds or through a short spacer (CH2, CH2S, CH2O, etc.), have been outlined. These synthetic approaches are of general character and can be used both individually and in combination to afford promising organoboron clusters of diverse architectures.

1 Introduction

2 C–C Cross-Coupling Strategies in the Synthesis of Azahetero­cyclic Carboranes

3 Carboryne-Based Transformation Strategies

4 Condensation Strategies: Reactions of Decaborane B10H14 with Substituted Acetylenes

5 Conclusion and Outlook

1-Nicotinoylbenzotriazole: A Convenient Tool for Site-Selective Protection of 5,7-Dihydroxycoumarins

1-Nicotinoylbenzotriazole (NicBt) was uncovered as an efficient protecting agent for the site-selective acylation of resorcinol-type phenolic groups with almost equal reactivity. The use of NicBt allows selective protection of the 7-OH group in 5,7-dihydroxycoumarins in one simple scalable step, while combination of the nicotinoylation with tosylation–denicotinoylation or silylation–denicotinoylation yields 5-OH-protected 5,7-dihydroxycoumarins. Furthermore, nicotinoylated 5,7-dihydroxycoumarins proved useful in a gram-scale three-step preparation of a 2,2-dimethylpyrano[2,3-f]coumarin, a key intermediate for the synthesis of calanolide A, an HIV reverse transcriptase and Mycobacterium tuberculosis inhibitor, and its active analogues.

Synthesis of enantiomerically pure 2-aryloxy carboxylic acids and their derivatives

Recent publications on the key preparation methods of the enantiomers of 2-aryloxy carboxylic acids are summarized and comparative analysis of the methods is given. The information is arranged according to the type of the starting compound, being classified into syntheses from enantiomerically pure chiral precursors and syntheses from prochiral precursors, which imply generation of an asymmetric centre in the substrate molecule. Data on the chemical resolution of racemic mixtures of the title compounds are addressed in a separate Section. Attention is focused on the preparation of practically valuable 2-aryloxy acids. Examples of biologically active derivatives of 2-aryloxy carboxylic acids are given.

The bibliography includes 121 references.