Synthetic Routes toward Asymmetrically Substituted (Functionalized) 4H-Cyclopenta[2,1-b:3,4-b ']dithiophenes

Abstract

A two-step synthetic protocol involving (i) a Wittig-type carbonyl olefination, and (ii) regioselective alkylation of the exocyclic double bond with LiAlH4 and an alkyl bromide, was developed as an alternative to the recently reported three-step synthetic approach toward asymmetrically substituted/functionalized 4H-cyclopenta[2,1-b:3,4-b]dithiophenes. The two routes are rather complementary, with specific advantages depending on the desired substitution pattern, and are of particular appeal for the construction of semiconducting materials to be applied in organic photovoltaics.