The syntheses of dimethyl 2, 2'-bithiophene-4, 4'-dicarboxylate (3), dimethyl 2, 2'- bithiophene-3, 4'-dicarboxylate (4), and dimethyl 2, 2'-bithiophene-3, 3'-dicarboxylate (5) are described. Single-crystal X-ray structural analysis of these compounds shows that the thiophene rings in 3 and 4 are nearly coplanar (dihedral angle close to 0°) and they adopt the anti sulfur conformation in the solid state. Further, the structure of 4 is in agreement ...
