Divergent synthesis of 3-substituted thieno[3,4-b]thiophene derivatives via hydroxy-based transformations

Herein, we have developed the first Pd-catalytic method for the preparation of 3-hydroxythieno[3,4-b]thiophene-2-carboxylate, which can be widely utilized as the chemical building block for modular assembly of structurally diverse 3-substituted thieno[3,4-b]thiophene derivatives via hydroxy-based transformation. Furthermore, we have evaluated the effect on their photophysical properties of the introduction of different substitutions at the C3-position and prepared conjugated polymers bearing 3-substituted thieno[3,4-b]thiophene units. We demonstrated that the photoluminescence (PL) properties of thieno[3,4-b]thiophene-2-carboxylate can be efficiently modulated by introducing different functional groups at the C3-position.