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Benzo[ b ] thiophene derivatives. XXII. Synthesis of the isomeric 5‐methyl‐6‐methoxy‐ and 5‐methoxy‐6‐methylbenzo[ b ] thiophene‐2‐carboxylic acids
Author(s) -
Campaigne E.,
Abe Yasuo
Publication year - 1975
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.5570120515
Subject(s) - chemistry , thiophene , methyl iodide , medicinal chemistry , hydrogen iodide , iodine , stereochemistry , organic chemistry
The two isomeric benzo[ b ] thiophene‐2‐carboxylie acids having methyl and methoxy groups at positions 5 and 6 have been prepared and characterized. Both acids have been decarboxylated to the corresponding isomeric 5,6‐disubstituted benzo[ b ]thophenes, and esterified to their methyl esters. The intermediate rhodanines, α‐mercaptocinnamic acids and corresponding disulfides are described. An unusual by‐product in the oxidative cyclization of β‐3‐methyl‐4‐methoxyphenyl‐α‐mercaptoacrylic acid with iodine is shown to be trans ‐3‐methyl‐4‐methoxycinnamic acid, which can also be formed directly from the mercaptoacrylic acid by reduction with hydrogen iodide.