Gytė Vilkauskaitė

Sonogashira Coupling Offers a New Synthetic Route to Thieno[2,3-c]pyrazoles

Abstract 1,3-Disubstituted-5-chloro-4-iodopyrazoles are selectively coupled with phenylacetylene under typical Sonogashira reaction conditions [PdCl2(PPh3)2, CuI, Et3N, dimethylformamide (DMF)] to obtain the corresponding 5-chloro-4-(phenylethynyl)pyrazoles in good yield. The latter are smoothly cyclized with Na2S in DMF into the corresponding thieno[2,3-c]pyrazoles. Detailed spectroscopic investigations (1H, 13C, and 15N NMR, mass, and infrared) of all compounds are reported.

4-{[(1-Phenyl-1H-pyrazol-3-yl)oxy]methyl}-1,3-dioxolan-2-one

The title compound was obtained by the reaction of tosylated glycerol carbonate with 1-phenyl-1H-pyrazol-3-ol in a good 71% yield. Detailed spectroscopic data (1H-NMR, 13C-NMR, 15N-NMR, IR, MS) are presented.

5-Chloro-4-iodo-1,3-dimethyl-1H-pyrazole

Reaction of 5-chloro-1,3-dimethyl-1H-pyrazole with I2/HIO3 in refluxing acetic acid gives the title compound in good yield. Detailed spectroscopic data (1H NMR, 13C NMR, 15N NMR, IR, MS) are presented.