Mykhailiuk selected the pyrazoles as a target because they serve as the core structure for commercial agrochemicals made by Syngenta, Bayer, and BASF. Mykhailiuk believes the new reagent also will help prepare difluoromethyl-substituted cyclopropanes, ketones, boronic acids, and other intermediates common in organic synthesis. In agrochemistry, difluoromethyl-substituted pyrazoles have been successful as succinate dehydrogenase enzyme inhibitors that disrupt the metabolism of disease-causing fungi. For example, Syngenta’s isopyrazam fungicide, introduced in 2011, controls diseases in wheat, bananas, and other crops. “However, there are few reagents and methods that enable the introduction of the –CHF2 functional group into heterocycles,” Syngenta’s Berthon says. “The present paper presents a novel and simple way to make difluoromethyl pyrazoles. I think this work just scratches the surface of what is possible, and I expect this report will be followed by a flurry of papers making new uses of this reagent.” /articles/93/i19/New-Reagent-Brings-Fresh-Approach.html 20150507 Synthesis: Fluorinated diazomethane serves up key difluoromethyl intermediates for drugs and agrochemicals News of The Week 93 19 /magazine/93/09319.html /departments/.html /collections/notw.html New Reagent Brings Fresh Approach To Fluorination Science & Technology Stephen K. Ritter In situ generation and trapping of difluoromethyl diazomethane opens up new opportunities to prepare chemical intermediates, such as difluorinated pyrazoles. SETTING A TRAP Reaction scheme showReaction sheme showing in situ generation of difluoromethyl diazomethane and subsequent trapping with an alkyne to make a fluorinated pyrazole.
by Stephen K. Ritter |
May 07, 2015