Diels-Alder reactions of vinyl derivatives of [1]benzothieno[3,2-b]furan

2-Vinyl- (2) and 3-vinyl[1]benzothieno[3,2-b]furan (3) react with dimethyl acetylenedicarboxylate, methyl propiolate, maleic anhydride, or acrylonitri le endo-selectively as dienes to afford new [1]benzothieno[3,2-b] [1]benzof uran derivatives 7-20. cis-Anhydrides 13 and 18 were transformed into dimet hyl eaters 21 and 22, respectively. It was shown that the base-catalyzed hy drolysis of 13 and 18 is accompanied by rearrangement of double bond in 13 and cis/trans isomerization of carboxylic group. Diesters 21 and 22, and ni triles 20 and 24 were aromatized by treatment with 2,3-dichloro-5,6-dicyano -1,4-benzoquinone. Selective monodecarboxylation of [1]benzothieno[3,2-b] [ 1]benzofuran-8,9-dicarboxylic acid (26) and [1]benzothieno[3,2-b] [1]benzof uran-6,7-dicarboxylic acid (27) afforded [1]benzothieno[3,2-b] [1]benzofura n-8-carboxylic acid (28) and [1]benzothieno[3,2-b] [1]benzofuran-7-carboxyl ic acid (29), respectively.