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Nucleophilic substitution of halopyridines by benzenethiolate anion via a radical chain mechanism
Author(s) -
Kondo Shuji,
Nakanishi Minoru,
Tsuda Kazuichi
Publication year - 1984
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.5570210466
Subject(s) - chemistry , scavenger , reactivity (psychology) , medicinal chemistry , nucleophile , radical nucleophilic aromatic substitution , substitution reaction , nucleophilic substitution , ion , electron transfer , azobenzene , photochemistry , nucleophilic aromatic substitution , radical , organic chemistry , molecule , catalysis , medicine , alternative medicine , pathology
2‐Halopyridines 1a‐d reacted with sodium thiophenoxide in DMF at 80° to afford the ipso ‐substitution products. The following relative order of reactivity was observed: 2‐iodopyridine ( 1a) ∼ 2‐bromopyridine ( 1b) ≫ 2‐chloropyridine ( 1c ) ∼ 2‐fluoropyridine ( 1d ). The reaction of 1b is inhibited by the electron scavenger azobenzene and by the radical scavenger benzoqoquinone. Furthermore, results of the reaction of 3‐bromopyridine ( 2b ) serve to rule out pyridyne mechanism. It is reasonable to suggest therefore that the reaction proceeds through the radical chain process containing one electron transfer, that is S RN 1.