Synthesis of Nitro-Substituted Thiophenes, Pyrroles, Dipyrroles and Tetrapyrroles
Document Type Theses, Ph.D
Successfully submitted for the award of Doctor of Philosophy (Ph.D.) to the Dublin Institute of Technology, 2012.
The synthesis of a number of 3-nitro-2-substituted thiophenes was performed via a tandem Michael/Henry reaction and employing solid phase microwave chemistry. The method was broadened to the synthesis of N-protected 3-nitro-2-substituted pyrroles. Unfortunately, application of the developed methodology to the analogous furan series synthesis was found to be unsuccessful. The new methodology possesses significant advantages over traditional protocols, not least that it obviates the need for a blocking group at the 5-position.The nitro group is particularly useful as it provides a handle for further functionalisation. The nitro-substituted pyrroles were employed in the synthesis of dipyrromethanes, which are key intermediates in the synthesis of -substituted porphyrins. However, deprotection of these products and of the pyrroles themselves could not be achieved and thus preparation of the porphyrins was not possible. A number of novel nitrosubstituted di- and tetrapyrroles was prepared and may have interesting biological activity, as antitumour agents for example. Traditional methodology for the synthesis of porphyrins was used to prepare a small library of novel porphyrin-endoperoxide hybrids. The N-protected 3-nitro-2-substituted pyrroles, their derivatives and the porphyrin-endoperoxide hybrids have been submitted for assessment of their biological activity and the results are eagerly awaited.