Shyh-Ming Yang, Jim-Min Fang
Feb 5, 2007
Citations
0
Influential Citations
9
Citations
Journal
Tetrahedron
Abstract
Abstract Our present study provides an expedient method for the synthesis of novel polycyclic and multi-substituted thiophene derivatives. A series of 4,5-di(hydroxyalkyl)-4,5-dihydrothiophene-2-carboxylates (e.g., 4a – c and 10 ) were prepared by the SmI 2 -promoted three-component coupling reactions of thiophene-2-carboxylate with aromatic aldehydes and 4-methoxyacetophenone. Diol 4a was oxidized by DDQ or pyridinium dichromate to give 5-acyl-4-hydroxyalkyl-4,5-dihydrothiophene-2-carboxylate 6a , which was subjected to dehydration to give either alkene 7 with terminal C C double bond or alkene 15a having conjugation with the ester group, depending on the reaction conditions using different quantities of p -toluenesulfonic acid. Alkene 7 underwent an intramolecular Friedel–Crafts alkylation to give a tetralone-fused thiophene-2-carboxylate 9 . By the similar procedure, a carbazole-fused thiophene 14 was also prepared. Alkenes 15a – c underwent autooxidative fragmentation to give 4,5-diacylthiophene-2-carboxylates 5a – c that were elaborated to pyridazine-fused thiophenes.