Synthesis of Mixed Thiophene-Pyrrole Heterocycles

The synthesis of mixed thiophene-pynule heterocycles has been reviewed.The systems under consideration are various isomeric thienylpynoles as well as tricyclic analogs containing non-condensed combinations of two or three pyrrole and thiophene units.10\ AcOH Me0 0 OMe 7 1 Kusharov and his coworkers3 were interested in studying the conformation and properties of 1-substituted pyrrole-2-carboxaldehydes and they synthesized I-(4J-dmethyl-2-thienyl)pyrrole-2-carboxaldehyde (4) as part of their invesdgation.Treatment of 2-amino-4,5-dimethylthiophene with 25-dithoxytetrahydrofm in glacial acetic acid gave 3, which was formylated by V~lsmeier reaction to give the corresponding aldehyde (4) in high yield.Experimental and calculated values of the dipole moment and Kerr constants were compared to determine the preferred conformation, based on steric interactions, of the carbonyl oxygen with respect to the N-atom of 4 and other substituted pymle-2-carboxaldehydes. AcOH