THIOPHENE SYSTEMS .2. SYNTHESIS AND CHEMISTRY OF SOME 4-ALKOXY-3-SUBSTITUTED THIOPHENE DERIVATIVES

Several 4-alkoxy-, 4-hydroxy- and 3-amino-disubstituted thiophenes were prepared as potentialintermediates for the preparation of novel thieno[3, 4]tricyclic systems. The 4-alkoxy-3-substituted thiophenes 8a, b were prepared by acid-catalyzed alcohol exchange of 4-hydroxythiophene7. Base stable thiophenes 8a, b were converted to acids 10a, b, amides lla, b, and hydrazide 12.Electrophilic substitution reactions with 10b occurred exclusively to give 5-substituted derivatives. Hydrazide 12 was converted via azide 17 to stable, electron-rich 4-ethoxy-3-thiopheneamine (23). 4-Alkoxythiophene derivatives 10a, b and 19 were converted to 4-hydroxy derivatives with boron tribromide. Intermediate and final compounds were examined for potential tautomerism. © 1979, American Chemical Society. All rights reserved.