Radical Reactions Enabled By Porphyrinoids

Abstract

“ Look deep into nature , and then you will understand everything better.” Albert Einstein Porphyrinoids, also known as the pigments of life, are a class of naturally occurring organic dyes. They play key roles in crucial processes that support life - oxygen transport (hem), electron transport (cytochrome c), photosynthesis (chlorophyll a), and synthesis of DNA (vitamin B12). Vitamin B12 - a co-factor in many catalytic processes. Following nature, we have been exploiting the potential of this compound in catalysis.Vitamin B12 - catalysis has been successfully translated into the laboratory and used in a small collection of reactions.[1-2] The advantage of using vitamin B12 as a catalyst lays in the complete stability of the central cobalt ion and by the definition it is nontoxic. It has also been well documented that the reaction mechanism usually follows a radical pathway, bringing a new dimension to this already interesting field.[2] Along this line, we have developed new vitamin B12-catalyzed reactions involving reduction of Co(III) to Co(I) or Co(II) and subsequent reactions with electrophiles or radicals. Vitamin B12 derivative unusually catalyzes a new olefinic sp2 C-H alkylation reaction with diazo reagents as a carbene source,[3], acylation of activated olefins, alkylation of strained molecules.[4-6] These key findings emphasize the unique feature of vitamin B12 as a catalyst to achieve something unachievable with other methodologies or to find a greener approach.