A New Efficient Synthesis of 4-Alkoxy-1,6-diaryl-1H-pyrazolo[3,4-d]pyrimidine Derivatives

Floro-pyrazolo[3,4-d]pyrimidine derivative as a novel plant activator induces two-pathway immune system

Plants are known to develop a multi-faceted innate immune system for pathogenic defense. Systemic acquired resistance (SAR) and induced systemic resistance (ISR) are the two main pathways. Many chemical inducers known as plant activators that activate innate immunity to defend against pathogens have been discovered. Currently, the exploitation of new plant activators is mainly done to develop analogs of salicylic acid as SAR-signaling molecules; however, the ISR pathway is hardly investigated for new plant activators. Based on recent studies on 1-methyl pyrazolo [3,4-d]pyrimidine bioactivity and ATP-induced resistance to biotrophic and necrotrophic pathogens, a new lead compound, 1-methyl-4-amino-pyrazolo [3,4-d]pyrimidine, was obtained as a new scaffold of plant activators for possible inducing ISR immunity system. Additionally, fluorine atom plays an important role in the design and development of new pesticides due to the unique physical chemistry effect, a series of pyrazolo [3,4-d]pyrimidine derivatives were designed and synthesized. Several compounds showed good broad-spectrum induced resistance in vivo, but there was no direct antibacterial activity in vitro. Notably, the introduction of fluorine atom at the para-position of the benzene ring greatly enhanced the induction activity of P1d both involved in SAR and ISR pathways, which implied the inducing resistance both in defending pathogens and insects.

Synthesis of Several New 1-arylpyrazolo[3,4-d]Pyrimidines Containing an Amide Moiety

A series of novel 1-arylpyrazolo[3,4-d]pyrimidine derivatives, containing an amide moiety, was synthesised by condensation of different acids with 1-(2,4-dichlorophenyl)-1H-pyrazolo[3,4-d]pyrimidin-4-amine. This intermediate was prepared from 5-amino-1-(2,4-dichlorophenyl)-1H-pyrazole-4-carbonitrile by condensation with triethyl orthoformate and then cyclisation with ammonium hydroxide solution in tetrahydrofuran at room temperature. In addition, the molecular structure of a 1-arylpyrazolo[3,4-d]pyrimidine containing an amide moiety was determined by single crystal X-ray diffraction.

Synthesis, Crystal Structure and bIological Activity of 5-(4-fluorophenyl)-N,N-dimethyl-7-(trifluoromethyl)Pyrazolo[1,5-a]Pyrimidine-3-carboxamide

The title compound, 5-(4-fluorophenyl)-N,N-dimethyl-7-(trifluoromethyl)pyrazolo[1,5-a]pyrimidine-3-carboxamide, has been synthesised by condensation of dimethylamine with 5-(4-fluorophenyl)-7-(trifluoromethyl)pyrazolo[1,5-a]pyrimidine-3-carboxylic acid. This intermediate was prepared from ethyl 5-amino-1H-pyrazole-4-carboxylate by cyclisation with 4,4,4-trifluoro-1-(4-fluorophenyl)butane-1,3-dione and then saponification with sodium hydroxide. The crystal structure of the title compound was determined. The compound possesses distinct effective inhibition on the proliferation of some cancer cell lines.

A convenient four-component one-pot strategy toward the synthesis of pyrazolo[3,4-d]pyrimidines

An efficient one-pot synthesis of pyrazolo[3,4-d]pyrimidine derivatives by the four-component condensation of hydrazines, methylenemalononitriles, aldehydes and alcohols has been developed via two different reaction pathways. The structures of target products were characterized by IR spectroscopy, NMR (¹H and ¹³C) spectroscopy and HRMS (ESI) spectrometry. The crystal structure of 4-ethoxy-6-(2-nitrophenyl)-1-phenyl-1H-pyrazolo[3,4-d]pyrimidine was determined by single crystal X-ray diffraction.