Hydrogen bond studies in chemically tuned pyrroles

CHED 582

Charles M. Baldwin, cbaldwin@uu.edu and Reilly M. Eason. Department of Chemistry, Union University, 1050 Union University Drive, Jackson, TN 38305
Previous research with the compound ethyl-1,2-dimethyl-4,5-diphenylpyrrole-3-carboxylate has shown that a hydrogen bond exists between the carbonyl oxygen of the carboxyethyl group at the 3-position and the methyl hydrogens at the 2-position in the pyrrole ring. The goal of the current research was the insertion of a methylene group between the carboxyethyl group and the pyrrole ring ostensibly moving the oxygen acceptor away from the hydrogen donor and altering the hydrogen bond interaction. Perturbations to the hydrogen bond would be assessed utilizing dynamic NMR, X-ray crystallography, and IR spectroscopy. To achieve the methylene group insertion, the original synthesis of ethyl-1,2-dimethyl-4,5-diphenylpyrrole-3-carboxylate was modified to synthesize the target compound, ethyl 2-(2-methyl-4,5-diphenyl-1H –pyrrol-3-yl)acetate. Synthesis of the target compound called for heating benzoin, ethyl levulinate, and ammonium acetate in glacial acetic acid. Evidence that the target compound had been synthesized was not obtained. Instead, all evidence pointed to the synthesis of 2,3,5,6-tetraphenyl-1,4-pyrazine.