Selective multiple magnesiations of the thieno[3,2-b]thiophene scaffold

A full functionalization of all four positions of the thieno[3,2-b]thiophene scaffold was achieved. Starting from 2,5-dichlorothieno[3,2-b]thiophene, magnesiation of the 3- and 6-position using tmpMgCl⋅LiCl furnishes, after trapping with various electrophiles, 3,6-difunctionalized dichlorothieno[3,2-b]thiophenes. Subsequent dechlorination and regioselective metalation or regioselective magnesium insertion into the CCl bond provides fully functionalized thieno[3,2-b]thiophenes. Furthermore, new condensed heterocycles and small oligomers of these compounds with potential applications in material chemistry have been prepared.