Synthesis of trifluoromethylated pyrido[2,3-d]pyrimidine-2,4-diones from 6-aminouracils and trifluoromethylated pyrazolo[3,4-b]-pyridines from 5-aminopyrazoles

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.

Trifluoromethyl Vinamidinium Salt as a Promising Precursor for Fused β-Trifluoromethyl Pyridines

An efficient chlorotrimethylsilane-promoted synthetic protocol for the preparation of functionalized fused β-trifluoromethyl pyridines by cyclization of electron-rich aminoheterocycles or substituted anilines with a trifluoromethyl vinamidinium salt was developed. The efficient and scalable approach for producing represented trifluoromethyl vinamidinium salt demonstrated huge prospects for further use. The structure specificities of the trifluoromethyl vinamidinium salt and their impact on the reaction progress were determined. The procedure's scope and alternative ways of the reaction were investigated. The possibility of increasing the reaction scale up to 50 g and further modification of obtained products was shown. A minilibrary of potential fragments for ¹⁹F NMR-based fragment-based drug discovery (FBDD) was synthesized.

Synthesis of Pyrazolo[3,4-b]Pyridine and Pyrido[2′,3′:3,4]Pyrazolo [1,5-a]Pyrimidine Derivatives

The synthesis of two series of 1-phenyl and 1 H-pyrazolo[3,4- b]pyridine is described. Thus, reacting 5-amino-1-phenylpyrazole with chalcone analogues gave 4,6-diarylpyrazolo[3,4- b]pyridine derivatives. While, reacting the same starting material with benzylidene derivatives of ethyl cyanoacetate and malononitrile resulted in 4-oxo and 4-aminopyrazolo[3,4- b]pyridine derivatives, respectively. The synthesis of 3-amino-4,6-diarylpyrazolo[3,4- b]pyridines starting from pyridine was also described. Thus, chlorination of 4,6-diarylpyridone derivatives and their subsequent cyclisation with hydrazine hydrate afforded 3-amino-4,6-diarylpyrazolo[3,4 -b]pyridines. Reaction of the latter compounds with acetylacetone, ethyl ethoxymethylenecyanoacetate and chalcone analogue gave the tricyclic pyrido[2′,3′: 3,4]pyrazolo[1,5- a]pyrimidines. The structures of the products were confirmed by spectral data.