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Derivation of fluorine‐containing pyridinedicarboxylates. III Regio‐selective anion chemistry at the 2‐ and 4‐position
Author(s) -
Chupp John P.,
Molyneaux John M.
Publication year - 1989
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.5570260645
Subject(s) - chemistry , lithium diisopropylamide , carbanion , electrophile , alkyl , electrophilic substitution , halide , lithium (medication) , medicinal chemistry , trifluoromethyl , silylation , organic chemistry , ion , catalysis , deprotonation , medicine , endocrinology
In contrast of Part II of the series, 4‐alkyl‐2‐(difluoromethyl)‐6‐(trifluoromethyl)‐3,5‐pyridinedicarboxylates, 1 , were reacted with various strength bases to effect regio‐selective reaction of electrophiles at either the benzylic carbanion of the 4‐position, or at the 2‐(difluoromethyl)carbanion. Weaker bases up to and including potassium butoxide or lithium bis(trimethylsilylamide) effected reaction of 1 at the 4‐position to produce 2 and 3 by Stobbe‐type condensations of aldehydes and ketones. In similar manner carbon disulfide, carbon dioxide, alkyl halides, silyl halides, and hexachloroethane produced the highly functionalized derivatives 4‐10. In contrast, use of lithium diisopropylamide and like bases selectively effected carbanion formation at the 2‐position to form, with the cited electrophiles and others, substitution products 11. The latter were further derived to the highly functional materials, 12‐19.