ChemInform Abstract: What Do we Know about Metalloporphyrin Catalytic Oxidations?

Abstract

While oxidation may be considered one of the nasty chemical events we are faced with, it is also an important useful reaction playing a fundamental role in the living processes whose control in 'man made' chemical reactivity is extremely relevant.Essential to the importance of oxidation on its role into the living processes is the smoothness and delicate control of the phenomenon allowing for its occurrence in a delicate tailored way.The first approach to mimicking natural oxidation involved the plain replay of the natural enzymatic oxidation using simple metalloporphyrins in the presence of an axial ligand and using the singular mono-oxygen donor iodosyl benzene. Such a simple model demonstrated the feasibility of the artificial approach.In a second generation of studies, far better catalysts and catalytic conditions were established.From those, considerable progress was made to the present day. Experimental and theoretical studies on the mechanism of the catalytic oxidations allowed for the development of very promising and useful reactions where the most desirable oxidants can be used to perform efficient and selective reactions providing that specific catalysts, oxidants and reaction conditions are properly selected.To the common man oxidation is a word of concern, without realising that besides the undesirable phenomena he associates to the word, oxidation is also a basic phenomenon he himself very much depends on. As a source of energy in the diverse spectacular combustion processes, but also in the peaceful chemical events which sustain life, his own life. We, as we are, would not be concerned with oxidation were it not for the importance of those quiet manifestations of oxidative processes.An admirable characteristic of the spirit of man is that if he starts to understand something, hardly stops to desire penetrating deeper and deeper in the knowledge of the facts. The reward is not only intellectual delight but also the capacity to manipulate nature to our own advantage.Combustion was a phenomenon known to primitive man. After chemistry has risen from the darkness of phlogiston establishing the importance of oxygen, the relationship between "fire combustions" and respiratory events came to light with the concept of "cold combustions". The story follows, and the desire to understand and mimic the oxidation enzymes and their performance made germinate an ambitious but sound research effort that has produced many important results.

Estudos oxidativos biomiméticos com os produtos naturais piperina e piplartina

“…Na tentativa de aperfeiçoar o uso das metaloporfirinas como modelo para sistemas biológicos, novos modelos produzidos a partir de modificações na Fe(TPP) foram testados (GONSALVES, 2002). Estes modelos evitam os processos de dimerização, que impedem a ligação do substrato ao metal da porfirina e melhoram a atividade catalítica do complexo intermediário (SUSLICK, 1999).…”