Synthesis of some novel pyrazolo[3,4-d]pyrimidine derivatives as potential antimicrobial agents

Preparation and chemistry of 3/5-halogenopyrazoles.

3.01 – Pyrazoles

A series of novel pyrazole oxime derivatives containing a 2-chloro-5-thiazolyl moiety were synthesized. Their structures were confirmed by (1)H NMR, (13)C NMR, and elemental analysis. The preliminary bioassays showed that all of the title compounds had low acaricidal activity against Tetranychus cinnabarinus . However, most of them exhibited excellent insecticidal activity against Aphis medicagini at the dosage of 0.5 mg/mL, and some compounds still showed good insecticidal activity against A. medicagini even at the dosage of 0.2 mg/mL. Meanwhile, some title compounds displayed fungicidal and plant growth regulatory activities.

Synthesis and Biological Activities of Novel Pyrazole Oxime Derivatives Containing a 2-Chloro-5-thiazolyl Moiety

Publisher Summary This chapter deals with the chemistry of five-membered ring fluorinated heterocycles. Fluorine and perfluoroalkyl groups positioned strategically in target molecules can considerably modify the chemical properties, biological activity, and selectivity. Fluoro-containing compounds play a significant role in medicinal and agricultural chemistry, as well as in material science. A number of fluoro and perfluoroalkyl-substituted pharmaceuticals, agrochemicals, dyes, and polymers are largely commercialized. Important differences in chemical reactivity of fluorinated compounds are based on the difference in: (1) carbon–fluorine, (2) carbon–hydrogen bond energy, and (3) electronegativity between fluorine and hydrogen. It is observed that fluorine introduced into biologically active molecules can block metabolism. There are two fundamentally different strategies, by which fluorine and perfluoroalkyl groups can be introduced into target molecules: (1) direct introduction that occurs by direct substitution of hydrogen by fluorine and perfluoroalkyl groups in a late step of the reaction sequence, and (2) introduction of fluorine and perfluoroalkyl groups by the application of fluorine-containing building blocks, derived from the readily available starting materials.

Fluoro Heterocycles with Five-Membered Rings

Syntheses and reactions of 2-halo-5-thiazolecarboxylates

Synthesis and 13C NMR of (trifluoromethyl)hydroxypyrazoles

Reaction of ethyl 4,4,4-trifluoroacetoacetate with methylhydrazine produced not only the previously reported 5-hydroxy-3-(trifluoromethyl)pyrazole 1 but also its unknown isomer the 3-hydroxy-5-(trifluoromethyl)pyrazole 4. The structure assignements are etablished based on 13 C NMR spectra. Compound 1 was converted to 5-chloro-3-(trifluoromethyl)pyrazolecarboxylic acid 3 in two steps.

Francis M. Schleppnik

Papers

Syntheses and reactions of 2-halo-5-thiazolecarboxylates

Synthesis and 13C NMR of (trifluoromethyl)hydroxypyrazoles

Synthesis and 13C NMR of (Trifluoromethyl)hydroxypyrazoles.