My students and I are interested in the broad field of synthetic organic chemistry. We are currently focused on exploring the synthesis and reactivity of a class of iron catalysts in oxidative and reductive organic transformations, and synthesizing polymers with photocleavable crosslinks with applications in temporary adhesives.
Development and Exploration of Iron Catalysts
We are broadly interested in developing air-stable (cyclopentadienone)iron carbonyl compounds as catalysts for reductive and oxidative transformations of organic compounds. Our interest in these compounds stems from their ease of synthesis, ease of handling, and the low cost (and high natural abundance) of iron. Iron compounds 1 and 2 were previously synthesized by Knölker, and we discovered that under certain conditions they are both active alcohol oxidation and carbonyl reduction catalysts (Scheme 1). We view these compounds as air-stable variants of Knölker’s air-sensitive iron hydride 3, which was shown to be an active transfer hydrogenation catalyst by Casey and Guan in 2007.
These iron compounds catalyze alcohol oxidations, carbonyl reductions, imine reductions, diol lactonizations, reductive aminations, and amine/alcohol coupling reactions (through a borrowing hydrogen mechanism), and it has been established that modifications to the cyclopentadienone substitution impact the reactivity of the catalyst. We are currently trying to determine how the substituents impact catalyst reactivity with a goal of rationally designing more active catalysts. We have synthesized a class of these catalysts where the cyclopentadienone substitution has been systematically modified and are exploring their reactivities in a series of oxidation and reduction reactions.
We are also exploring hydrogen acceptors other than acetone. A major advantage of transfer dehydrogenations is their lack of a strong oxidant, but the oxidation potential of acetone is such that the equilibrium for the oxidation of many alcohols is not favored. We are looking at biomass-derived hydrogen acceptors with a goal of developing a sustainable oxidation process that has a wide substrate scope.