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Tetracyclic phenothiazines. III. . Intermolecular hydride transfer in acid induced disproportionation of 1,2‐dihydro‐3‐hydroxy‐3 H ‐pyrido[3,2,1‐ kl ] phenothiazines
Author(s) -
Martin A. R.,
Kim S. H.,
Peng G. W.,
Siegel G. V.,
Yale T. J.
Publication year - 1978
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.5570150817
Subject(s) - chemistry , sodium borohydride , disproportionation , borohydride , phenothiazine , medicinal chemistry , stereochemistry , organic chemistry , catalysis , medicine , pharmacology
1,2‐Dihydro‐3‐hydroxy‐3 H ‐pyrido[3,2,1‐ kl ]phenothiazines and 1 H ‐pyrido[3,2,1 ‐kl ]phenothiazines undergo acid catalyzed disproportionation with intermolecular hydride transfer to form pyrido[3,2,1‐ kl ]phenothiazinium salts and 1,2‐dihydro‐3 H ‐pyrido[3,2,1‐ kl ]phenothiazines. Sodium borohydride reduction of 3‐alkyl‐ or 3‐arylpyrido[3,2,1‐ kl ]phenothiazinium salts gives 3‐alkyl‐ or 3‐aryl‐1 H ‐pyrido[3,2,1‐ kl ]phenothiazines. In the presence of a proton source, borohydride reduction of pyrido[3,2,1‐ kl ]phenothiazinium fluoroborate or 3‐chloropyrido‐[3,2,1‐ kl ]phenothiazinium perchlorate gives 1,2‐dihydro‐3 H ‐pyrido[3,2,1‐ kl ]phenothiazine, while 1 H ‐pyrido[3,2,1‐ kl ]phenothiazine is formed in aprotic solvents with pyridine present.