A zinc-catalyzed synthesis of 3-trifluoromethyl-4-trifluoroacetyl pyrazoles

Recent advances in the synthesis of trifluoromethyl-containing heterocyclic compounds via trifluoromethyl building blocks

Trifluoromethylated heterocyclic compounds have played an increasingly significant role in pharmaceuticals, agrochemicals, and materials. This is because the introduction of trifluoromethyl could enhance the lipophilicity, metabolic stability, and pharmacokinetic properties of heterocyclic drug molecules. Therefore, the synthesis of trifluoromethylated heterocyclics has become a major subject of research. The construction of trifluoromethylated heterocyclics via the annulation of trifluoromethyl building blocks with suitable partners has been proved to be a powerful strategy. In this review, we systematically summarize and discuss recent advances in the preparation of trifluoromethyl-containing heterocyclics via trifluoromethyl building block strategies over the period from 2019 to the present.

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.

Electrochemical Synthesis of Polysubstituted Sulfonated Pyrazoles via Cascade Intermolecular Condensation, Radical-Radical Cross Coupling Sulfonylation, and Pyrazole Annulation

Electrochemical synthesis of polysubstituted sulfonated pyrazoles from enaminones and sulfonyl hydrazides was established under metal-free, exogenous-oxidant-free, and mild conditions. By judicious choice of different electrochemical reaction conditions, NH₂-functionalized enaminones or N,N-disubstituted enaminones can react with aryl/alkyl sulfonyl hydrazides to afford tetra- or trisubstituted sulfonated pyrazoles in moderate to good yields, respectively. The gram-scale electrochemical transformation demonstrated the efficiency and practicability of this synthetic strategy. In addition, the sulfonated NH-pyrazole can be obtained via the dissociation of the N-tosyl group. Mechanistic studies reveal that the electrochemical cascade reaction synthesis of polysubstituted sulfonated pyrazoles proceeded via the sequence of intermolecular condensation, radical-radical cross coupling sulfonylation, and pyrazole annulation.