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Efficient Synthesis of 4‐Fluoro‐5‐(perfluoroalkyl)pyrazoles from Organofluorosilicon Building Blocks
Author(s) -
Bouillon JeanPhilippe,
Didier Benoît,
Dondy Boniface,
Doussot Pascale,
PlantierRoyon Richard,
Portella Charles
Publication year - 2001
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/1099-0690(200101)2001:1<187::aid-ejoc187>3.0.co;2-g
Subject(s) - chemistry , methylhydrazine , pyrazole , regioselectivity , fluorine , reagent , ring (chemistry) , organic chemistry , indazole , medicinal chemistry , catalysis , phenylhydrazine
A series of 4‐fluoro‐5‐(perfluoroalkyl)pyrazoles has been prepared by heterocyclization of hemiperfluoroenones 3 or synthetic equivalents 1 and 2 with methylhydrazine. Compounds 1−3 were obtained by reaction of acylsilanes and perfluoroorganometallic reagents. The fluorinated pyrazoles could also be prepared in a one‐pot reaction from the starting acylsilanes. This method is very general and has been applied to aromatic, aliphatic and carbohydrate derivatives, as well as to bis(pyrazole) derivatives. The reaction is completely regiospecific and the regiochemistry has been determined by HMBC correlations, 19 F‐ 1 H and 1 H‐ 1 H NOE and by comparison of chemical shifts and carbon‐fluorine coupling constants of ring pyrazole carbon and fluorine atoms.