“Reported, but Still Unknown.” A Closer Look into 3,4-Bis- and 3,4,5-Tris(trifluoromethyl)pyrazoles

Trifluoromethyl-β-dicarbonyls as Versatile Synthons in Synthesis of Heterocycles

Trifluoromethyl group relishes a privileged position in the realm of medicinal chemistry because its incorporation into organic molecules often enhances the bioactivity by altering pharmacological profile of molecule. Trifluoromethyl-β-dicarbonyls have emerged as pivotal building blocks in synthetic organic chemistry due to their facile accessibility, stability and remarkable versatility. Owing to presence of nucleophilic and electrophilic sites, they offer multifunctional sites for the reaction. This review covers a meticulous exploration of their multifaceted role, encompassing an in-depth analysis of mechanism, extensive scope, limitations and wide-ranging applications in diverse organic synthesis, covering the literature from the 21st century. This comprehensive review encapsulates the applications of trifluoromethyl-β-dicarbonyls and their synthetic equivalents as precursors of complex and diverse heterocyclic scaffolds, fused heterocycles and spirocyclic compounds having medicinal and material importance. Their potent synthetic utility in cyclocondensation reactions with binucleophiles, cycloaddition reactions, C-C bond formations, asymmetric multicomponent reactions using classical/solvent-free/catalytic synthesis have been presented. Influence of unsymmetrical trifluoromethyl-β-diketones on regioselectivity of transformation is also reviewed. This review will benefit the synthetic and pharmaceutical communities to explore trifluoromethyl-β-dicarbonyls as trifluoromethyl building blocks for fabrication of heterocyclic scaffolds having implementation into drug discovery programs in the imminent future.

In situ studies of reversible solid-gas reactions of ethylene responsive silver pyrazolates

Solid-gas reactions and in situ powder X-ray diffraction investigations of trinuclear silver complexes {[3,4,5-(CF3)3Pz]Ag}3 and {[4-Br-3,5-(CF3)2Pz]Ag}3 supported by highly fluorinated pyrazolates reveal that they undergo intricate ethylene-triggered structural transformations in the solid-state producing dinuclear silver-ethylene adducts. Despite the complexity, the chemistry is reversible producing precursor trimers with the loss of ethylene. Less reactive {[3,5-(CF3)2Pz]Ag}3 under ethylene pressure and low-temperature conditions stops at an unusual silver-ethylene complex in the trinuclear state, which could serve as a model for intermediates likely present in more common trimer-dimer reorganizations described above. Complete structural data of three novel silver-ethylene complexes are presented together with a thorough computational analysis of the mechanism.

Filling the gap with a bulky diaryl boron group: fluorinated and non-fluorinated copper pyrazolates fitted with a dimesityl boron moiety on the backbone

Successful synthesis has been reported of 4-Mes2B-3,5-(CF3)2PzH and 4-Mes2B-3,5-(CF3)2PzH bearing sterically demanding diarylboron moieties at the pyrazole ring 4-position, and their corresponding copper(I) pyrazolate complexes. They show visible blue photoluminescence in solution. The X-ray crystal structures revealed that the fluorinated {[4-BMes2-3,5-(CF3)2Pz]Cu}3 crystallizes as discrete trinuclear molecules whereas as the non-fluorinated {[4-BMes2-3,5-(CH3)2Pz]Cu}3 forms dimers of trimers with two close inter-trimer Cu⋯Cu separations. The solid {[4-BMes2-3,5-(CF3)2Pz]Cu}3 featuring a sterically confined Cu3N6 core displays bright blue phosphorescence while {[4-BMes2-3,5-(CH3)2Pz]Cu}3, which is a dimer of a trimer, is a red phosphor at room temperature. This work illustrates the modulation of photo-physical properties of metal pyrazolates by adjusting the supporting ligand steric features and introducing secondary diarylboron luminophores. Computational analysis of the structures and photophysical properties of copper complexes are also presented.

Synthesis of Highly Functionalized 4-Amino-2-(trifluoromethyl)-1H-pyrroles

In this work, the reactivity of 5-bromo-1,1,1-trifluoro-4-methoxypent-3-en-2-one toward primary aliphatic amines was studied. The reaction was found to be extremely selective to synthesize a series of 1-alkyl-4-(aminoalkyl)-2-(trifluoromethyl)-1H-pyrroles (13 examples, up to 90% yield) and a series of highly functionalized β-enaminones (6 examples, up to 78% yield), with only the amount of amine and the reaction conditions needing to be controlled. The structure of the products was unambiguously determined by single crystal X-ray diffraction and 2D NMR experiments.

Synthesis, molecular docking studies, and larvicidal activity evaluation of new fluorinated neonicotinoids against Anopheles darlingi larvae

Anopheles darlingi is the main vector of malaria in Brazil, characterized by a high level of anthropophilia and endophagy. Imidacloprid, thiacloprid, and acetamiprid are the most widespread insecticides of the neonicotinoid group. However, they produce adverse effects on the non-target insects. Flupyradifurone has been marketed as an alternative to non-fluorinated neonicotinoids. Neonicotinoids containing trifluoroacethyl substituent reveal increased insecticidal activity due to higher hydrophobicity and metabolic stability. We synthesized novel neonicotinoid insecticides containing fluorinated acceptor groups and their interactions were estimated with the nicotinic acetylcholine receptor (nAChR) binding site by molecular docking studies, to evaluate their larvicidal activity against A. darlingi, and to assess their outdoor photodegradation behavior. New neonicotinoid analogues were prepared and characterized by NMR and mass-spectrometry. The synthesized molecules were modelled by time-dependent density functional theory and analyzed, their interaction with nAChR was investigated by molecular docking. Their insecticide activity was tested on Anopheles larvae collected in suburban area of Manaus, Brazil. Four new fluorinated neonicotinoid analogs were prepared and tested against 3rd instars larvae of A. darlingi showing high larvicidal activity. Docking studies reveal binding modes of the synthesized compounds and suggest that their insecticidal potency is governed by specific interactions with the receptor binding site and enhanced lipophilicity. 2-Chloro-5-(2-trifluoromethyl-pyrrolidin-1-ylmethyl)pyridine 5 showed fast degradation in water maintaining high larvicidal activity. All obtained substances possessed high larvicidal activity in low concentrations in 48 hours of exposure, compared to commercial flupyradifurone. Such activity is connected to a unique binding pattern of the synthesized compounds to insect's nAChR and to their enhanced bioavailability owing to introduction of fluorinated amino-moieties. Therefore, the compounds in question have a high potential for application as control agents for insects transmitting tropical diseases, and they will be less persistent in the environment.

Deoxofluorination of (Hetero)aromatic Acids

Diverse trifluoromethyl-substituted compounds were synthesized by deoxofluorination of cinnamic and (hetero)aromatic carboxylic acids with sulfur tetrafluoride. The obtained products were used as starting materials in the preparation of novel fluorinated amino acids, anilines, and aliphatic amines - valuable building blocks for medicinal chemistry and agrochemistry.

Copper-catalyzed chemoselective synthesis of 4-trifluoromethyl pyrazoles

A series of 4-trifluoromethyl pyrazoles have been prepared via the copper-catalyzed cycloaddition of 2-bromo-3,3,3-trifluoropropene with a variety of N-arylsydnone derivatives under mild conditions. This new protocol under optimized reaction conditions [Cu(OTf)₂/phen, DBU, CH₃CN, 35 °C] afforded 4-trifluoromethyl pyrazoles in moderate to excellent yields with excellent regioselectivity.

A copper-catalyzed chemoselective synthesis of 4-trifluoromethyl pyrazoles via cycloaddition of 2-bromo-3,3,3-trifluoropropene with N-arylsydnones has been developed.

CFA-15 – a perfluorinated metal–organic framework with linear 1-D CuII-chains containing accessible unsaturated, reactive metal centres

The synthesis and crystal structure of the perfluorinated metal–organic framework CFA-15, CuII3(tfpc)₂(OH)₂·DMF, and the organic ligand H₂-tfpc, 3,5-bis(trifluoromethyl)-1H-pyrazole-4-carboxylic acid, are described.

CFA-13 - a bifunctional perfluorinated metal-organic framework featuring active Cu(i) and Cu(ii) sites

The synthesis and crystal structure of the mixed-valent perfluorinated metal-organic framework (Me₂NH₂)[CFA-13] (Coordination Framework Augsburg University-13), (Me₂NH₂)[CuCu(tfpc)₄] (H₂-tfpc = 3,5-bis(trifluoromethyl)-1H-pyrazole-4-carboxylic acid) is described. The copper-containing MOF crystallizes in the monoclinic crystal system within the space group P2₁/n (no. 14) and the unit cell parameters are as follows: a = 22.3887(19), b = 13.6888(8), c = 21.1804(13) Å, β = 90.495(3)°, V = 6491.0(8) ų. (Me₂NH₂)[CFA-13] features a porous 3-D structure constructed from two types of secondary building units (SBUs). Besides novel trinuclear [Cu(pz)₄]^- coordination units, the network also exhibits Cu(ii) paddle-wheel SBUs. (Me₂NH₂)[CFA-13] is fully characterized by single crystal X-ray diffraction, thermogravimetric analysis, variable temperature powder X-ray diffraction, IR spectroscopy, photoluminescence, gas sorption measurements and pulse chemisorption experiments. M[CFA-13] (M = K⁺, Cs⁺) frameworks were prepared by postsynthetic exchange of interchannel dimethylammonium cations. Moreover, it was shown that CO molecules can be selectively bound at Cu(i) sites of [Cu(pz)₄]^- units, whereas Cu(ii) paddle-wheel units bind selectively NH₃ molecules.

Polyfluoroalkylated 2-ethoxymethylene- 3-oxo esters: synthesis and chemical properties overview

The review focuses on the synthesis and chemical properties of polyfluoroalkylated 2-ethoxymethylene-3-oxo esters. The scope and peculiarities of their use as organic reagents in reactions with various N-, C-, O-, mono- and dinucleophiles are discussed in detail. The high reactivity of such derivatives is employed in the construction of enaminoketone, arene and heterocycle frameworks. Particular attention is paid to applications of these building blocks as chemicals for fine organic synthesis, bioactive compounds and metal complexes synthesis.

Copper-Mediated Domino Cyclization/Trifluoromethylation/Deprotection with TMSCF3: Synthesis of 4-(Trifluoromethyl)pyrazoles

A copper-mediated synthesis of 4-(trifluoromethyl)pyrazoles is described. In one step from readily accessible α,β-alkynic tosylhydrazones, a remarkable domino sequence of cyclization, trifluoromethylation, and detosylation takes place to furnish the 4-CF₃ N-H pyrazole cores with good functional group compatibility. The reaction conditions are mild and convenient, at room temperature in air, using the commercially available trifluoromethyltrimethylsilane (TMSCF₃) as the CF₃ source. The method can be applied to the synthesis of a 4-CF₃ analogue of the anti-inflammatory drug celecoxib.

Heptafluoroisopropyl diazomethane (i-C3F7CHN2): in situ generation and synthesis of pyrazoles

A novel chemical reagent, heptafluoroisopropyl diazomethane (i-C₃F₇CHN₂), has been generated in situ in aqueous media. It reacts with electron-deficient alkynes towards polyfluorinated pyrazoles that are important in agrochemistry.

High-Z′ structures of organic molecules: their diversity and organizing principles

A list has been compiled of 284 well determined organic structures having more than four crystallographically independent molecules or formula units (i.e. Z′ > 4). Another 22 structures were rejected because the space group or unit cell was probably misassigned; the rate for that type of error is then only 7%. The space-group frequencies are unusual; half the structures are in Sohncke groups, partly because the fraction of enantiopure structures of resolvable enantiomers is higher than for lowerZ′ structures. Careful investigation of the 284 structures has shown that they are very diverse; no simple classification can describe them all. Organizing principles have, however, been recognized for almost all of them. The most common features are simple modulations and hydrogen-bonded aggregates; only 14% of the structures have neither. In 50% of the structuresnmolecules are related by a pseudotranslation that would be a crystallographic translation but for small molecular displacements and rotations. In 70% of the structures there are aggregates (e.g. n-mers, columns or layers) held together by strong intermolecular interactions; those aggregates usually have approximate local symmetry. Because then-fold modulations and then-mers often haven<Z′, 85% of the structures withZ′ > 5 have several features that combine to give the highZ′ value. The number of different molecular conformations is usually small,i.e.one or two in 84% of the structures. More exotic packing features, such as ordered faults and alternating layers of different types, are found inca30% of the structures. A very few structures are so complex that it is difficult to understand how the crystals could have formed.

Synthesis, insecticidal activities and structure-activity relationship studies of novel anthranilic diamides containing pyridylpyrazole-4-carboxamide

BACKGROUND

Anthranilic diamide insecticides containing pyridylpyrazole-5-carboxamide are extremely important in modern agriculture. New structurally modified compounds with high insecticidal activity were discovered by designing a series of novel pyridylpyrazole-4-carboxamides (9I to 9IV) and pyridylpyrazole-4-carboxamides (10I to 10IV), the latter designed by the cyclisation of two amides. The structure-activity relationship (SAR) between the two series is of interest.

RESULTS

Two series of novel anthranilic diamides containing pyridylpyrazole-4-carboxamide were synthesised and characterised via melting point, (1)H NMR, (13)C NMR, MS and elemental analyses. The insecticidal activities of these compounds against Plutella xylostella were evaluated. At a concentration of 100 mg L(-1), the compounds with unmodified amide moieties (9I to 9IV) exhibited much better larvicidal activities than the other derivative compounds (10I to 10IV). Most of the compounds 9I to 9IV showed over 90% larvicidal activity at 100 mg L(-1). Furthermore, compounds 9IIIa, 9IIIc, 9IIId and 9IVd displayed significant insecticidal activity at 10 mg L(-1). Density functional theory (DFT) calculation was carried out to provide more information regarding SAR.

CONCLUSION

Thirty-two new anthranlic diamides containing pyridylpyrazole-4-carboxamide were designed and obtained. SAR analysis and DFT calculation results revealed that the amide moiety had a very important effect on bioactivity. This work has provided information that could aid investigations of novel insecticides.

Three-component synthesis of C2F5-substituted pyrazoles from C2F5CH2NH2·HCl, NaNO2 and electron-deficient alkynes

A one-pot reaction between C₂F₅CH₂NH₂·HCl, NaNO₂ and electron-deficient alkynes gives C₂F₅-substituted pyrazoles in excellent yields. The transformation smoothly proceeds in dichloromethane/water, tolerates the presence of air, and requires no purification of products by column chromatography. Mechanistically, C₂F₅CH₂NH₂·HCl and NaNO₂ react first in water to generate C₂F₅CHN₂, that participates in a [3 + 2] cycloaddition with electron-deficient alkynes in dichloromethane.

Efficient one-pot synthesis of 5-perfluoroalkylpyrazoles by cyclization of hydrazone dianions

A highly selective and efficient method for the synthesis of 5-trifluoromethylated and 5-perfluoroalkylated pyrazoles has been developed which relies on the cyclization of hydrazine dianions with ethyl perfluorocarboxylates.

Three-component synthesis of fluorinated pyrazoles from fluoroalkylamines, NaNO2 and electron-deficient alkynes

Three-component synthesis of fluorinated pyrazoles.

Pd(ii)-catalyzed ligand controlled synthesis of pyrazole-4-carboxylates and benzo[b]thiophene-3-carboxylates

A simple change of the ligand and solvent allows controlled, effective switching between cyclization–carbonylation–cyclization-coupling (CCC-coupling) and cyclization–carbonylation reactions.

Perfluorinated 1H-indazoles and hydrotris(indazol-1-yl)borates. Supramolecular organization and a new synthetic procedure to form scorpionate ligands

The molecular and supramolecular structures of new perfluorinated indazoles and hydrotris(indazolyl)borates reveal various types of intra- and intermolecular interactions and organizations.

Trifluoromethyl ketones: properties, preparation, and application

Trifluoromethyl ketones (TFMKs) are exceedingly valuable synthetic targets in their own right and as synthons in the construction of fluorinated pharmacons. This Feature Article provides an overview of the properties of TFMKs, an in-depth discussion of the methods available for their synthesis, and two illustrative examples of their application as key intermediates in medicinal chemistry.