Correlation of electronic structure to iron catalyzed C-H bond functionalization

Harvard University, Cambridge MA

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Abstract

? DESCRIPTION (provided by applicant): Correlation of electronic structure to iron catalyzed C-H bond functionalization In the field of homogenous catalysis, few reports have appeared offering general, chemically mild methods for the introduction of nitrogen- or oxygen-containing functional groups into simple hydrocarbon substrates. The ability to selectively incorporate functionality into unactivated C-H bonds represents a significant advance in converting inexpensive chemical feed stocks (e.g. hydrocarbons) to value-added functional molecules. However, the oxidative substitution of C-H bonds with amines or other functional groups often requires preoxidation of substrate or employs strong chemical oxidants in concert with atom or group transfer processes. A streamlined synthesis for functionalized products (e.g. N-heterocycles) with minimal or complete absence of waste generation would have tremendous impact on the synthesis of fine chemicals and pharmaceuticals. Towards this end, we have synthesized a class of electrophilic complexes featuring transiently-formed, or metastable metal-ligand multiple bonds capable of mediating C-H bond functionalization. Using dipyrrin ligand platforms as truncated models of the porphyrin platform found in P450 hydroxylase enzymes, we have observed reactivity from the ferrous-ligand constructs mirrors their porphyrin analogues. Catalytic C-H bond amination and olefin aziridination have been observed from the reaction of organic azides with simple iron(II) and iron(I) coordination complexes. The iron-catalyzed amination reaction is tolerant to a variety of organic azide precursors and has shown reactivity with a range of organic substrates to form N- heterocyclic products: linear azides can be intramolecularly aminated to form both pyrrolidine and piperidine structures, bearing an array of a-functional groups. The broader scientific impact of the proposed research can be summarized as the following: we will improve our understanding of factors contributing to the promotion of productive C-H bond activation and functionalization, further developing new classes of inorganic/organometallic catalysts to synthesize value-added commodity chemicals via clean reaction routes with minimal waste product.