Professor Spencer P. Pitre

Dr. Spencer P. Pitre
Assistant Professor
Oklahoma State University
Abstract

Nucleophilic Cobalt Photocatalysis and Organic Photoreductants: Two Enabling Approaches to Organic Synthesis

While carbon-centered radicals have become an increasingly important tool in organic synthesis, the breadth of radical precursors available to synthetic chemists remains underdeveloped. Many of the radical precursors employed in these methods require pre-functionalization of the initial feedstock chemical, adding undesired synthetic steps while generating additional byproducts after radical formation. Our lab’s research focuses on the development and advancement of nucleophilic cobalt photocatalysis and organic photoreductants, with the unifying theme of these programs being the expansion of the breadth of carbon radical precursors available to practitioners of the field. Our nucleophilic cobalt photocatalysis strategy leverages the unique reactivity of cobalt square planar complexes, like Vitamin B12, which can engage with electrophiles in SN2 reactions, generating Co(III)-alkyl intermediates that can be photolyzed under visible-light irradiation to generate carbon-centered radicals. Our contributions in this area leverage 1,2-dichloroalkyl electrophiles for the preparation of cyclopropanes. Our lab also focuses on utilizing organic photoreductants, such as halogen-bonding photocatalysts and organic anions, for the generation of carbon-radicals from alkyl and aryl halides and carbonyl compounds, circumventing the use of tin hydrides and ground state metal reductants generally required for activation of these substrates. Our contributions leveraging substituted hydroquinone photocatalysts and 1,4-dihydropyridine anions as organic photoreductants will be presented.

Spencer P. Pitre

Spencer was born and raised in the small Canadian province of Prince Edward Island. In 2012, he completed his B.Sc. with Honours in Chemistry at the University of Prince Edward Island with a minor in Physics. During his time at UPEI, he worked in the lab of Dr. Brian Wagner, focusing on structure-activity relationships of modified β-cyclodextrins for host- guest chemistry. As an undergraduate, Spencer also spent time at the National Research Council of Canada in Ottawa working under the supervision of Dr. Linda Johnston, where he studied the photo-uncaging of ceramides in supported lipid bilayers. In 2012, Spencer joined the group of Juan (Tito) Scaiano at the University of Ottawa as a Ph.D. student. His research in the Scaiano group focused on developing metal- free alternatives for visible-light photoredox catalysis, developing new mechanistic tools for characterization of photochemically-initiated chain reactions, and using heterogeneous semiconductors to catalyze photoredox transformations. After graduating from uOttawa in 2017, Spencer escaped the cold Canadian winters by joining the lab of Larry Overman at the University of California, Irvine as a NSERC Postdoctoral Fellow. Spencer’s research in the Overman lab focused on utilizing tertiary alcohols as radical precursors for the alkylation of medicinally relevant heterocycles and developing a Lewis acid catalyzed 1,4-radical addition reaction. In 2019, Spencer joined Oklahoma State University as an assistant professor, where he is interested in exploring new reactivity regimes in photoredox and cobalt catalysis.

Hosted by Professor Alexander Grenning