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Solvent‐free fluorination of partially‐chlorinated heterocyclics: Synthesis of 2,6‐difluoropyridine from 2,6‐dichloropyridine
Author(s) -
Boudakian Max M.
Publication year - 1968
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.5570050515
Subject(s) - chemistry , halogen , yield (engineering) , solvent , potassium fluoride , alkali metal , fluoride , halogenation , organic chemistry , inorganic chemistry , alkyl , materials science , metallurgy
Previous studies on the solvent‐free fluorination of partially‐chlorinated heterocyclics such as 2‐chloropyridine, 2,3,4,6‐ and 2,3,5,6‐tetrachloropyridine, and 2,4,6‐trichloropyrimidine with alkali metal fluorides or hifluorides revealed an inconsistent product pattern: degradation, partial or complete halogen exchange could occur. The present study concerned application of the solvent‐free halogen exchange technique (potassium fluoride) to 2,6‐dichloropyridine (I). The latter, as well as its fluorination products, exhibited good stability at 400° to provide an 80% yield of 2,6‐difluoropyridine (III). Moderation of fluorination conditions also permitted isolation of the precursor, 2‐chloro‐6‐fluoropyridine (II), a new compound. The above solvent‐free process to III is superior to the previously‐reported halogen‐exchange route in dimethyl sulfone solvent on the basis of yield, reaction time and number of processing steps.