Novel catalysis by metalloporphyrins

Abstract

Metalloporphyrins have long been known to be effective catalysts for a variety of organic reactions. These include cyclopropanation, epoxidation, and aziridination of olefins. Iron porphyrins are also efficient catalysts for the olefination of aldehydes and ketones in the presence of triphenylphosphine. This suggested to us that iron porphyrins may have the potential to mediate a variety of other processes. The work described in this dissertation broadly extends the reactions catalyzed by iron(III) tetraphenylporphyrin chloride, Fe(TPP)Cl. We have found that Fe(TPP)Cl is an efficient catalyst for N-H insertion reactions, C-H activation and the Buchner reaction between diazo reagents and arenes. These studies have also led to the development of efficient syntheses of piperazinones and morpholinones. N-H insertion reactions of a variety of aliphatic and aromatic amines were catalyzed by Fe(TPP)Cl using ethyldiazoacetate (EDA) as a carbene source with yields ranging from 68-97%. Primary amines were able to undergo a second insertion when another equivalent of EDA was added by slow addition. N-Heterocyclic compounds were poor substrates giving low yields or no N-H insertion products. Competition reactions and linear free energy relationships provided mechanistic insights for the insertion reaction. An attempt to achieve C-H insertions using EDA and Fe(TPP)Cl led to formation of maleate and fumarate dimers. However, using Fe(III), Cu(II) and Ag(II) porphyrin complexes and carbenes transferred from methyl diazomalonate produced both benzylic and aromatic C-H insertions products