One active area of research revolves around problems in biomass conversion. Here we seek to convert biorenewable carbon sources such as cellulose into high-value chemicals, which are currently accessed from petroleum roots. Our focus is on chiral chemicals rather than fuels as the former are far more valuable than the latter. Since the most valuable chemicals are partially oxidized, they have traditionally been accessed by the oxidation of petroleum resources. Biomass, by comparison, is an over-oxidized source of carbon (each carbon in glucose is at the alcohol or aldehyde oxidation state), and so one requires chemistries that selectively deoxygenate these feedstocks without stripping away all of the inherent chirality of the carbohydrates.
Since every carbon atom is oxygenated in a sugar, the problem reduces to achieving site-selective deoxygenation catalysis. We have targeted a non-eliminative solution (which necessarily loses one or two stereocenters) and have achieved this with non-transition metal catalysts for the activation of silanes. The fluoroaryl borane catalyst B(C6F5)3 (BCF) is unique in its ability to heterolytically activate silanes (into Si+ and H– equivalents), which has enabled site-selectively deoxygenation of cellulosic feedstocks. We have also discovered that BCF can activate hydro-boranes in the same way as hydro-silanes for deoxygenation chemistry, and their unique coordination chemistry provides a route for achieving different C–O bond activation selectivities. This Venn diagram shows the compounds we have synthesized in a single step from a primary biorenewable (glucose, sorbitol, isosorbide, etc).
- “Switching between X‑Pyrano‑, X‑Furano‑, and Anhydro‑X‑pyranoside Synthesis (X = C, N) under Lewis acid Catalyzed Conditions” Seo, Y.; Lowe, J. M.; Romano, N.; Gagné, M. R. Org. Lett. 2021, Article ASAP
- “Modulating Electrostatic Interactions in Ion Pair Intermediates To Alter Site Selectivity in the C-O Deoxygenation of Sugars” Lowe, J. M.; Bowers, B. E.; Seo, Y.; Gagné, M. R. Angew. Chem. Int. Ed. 2020, 59, 17297-17300.
- “Controlling Sugar Deoxygenation Products from Biomass by Choice of Fluoroarylborane Catalyst.” Seo, Y.; Lowe, J.; Gagné, M.R. ACS Catal. 2019, 9, 6648-6652.
- “Silylium (R3Si+) catalyzed condensative cyclization for anhydrosugar synthesis” Y. Seo, M. R. Gagné, ACS Catalysis 2018, 8, 6993-6999.
- “Boron-Catalyzed Reduction of Carbohydrate Derivatives with Catecholborane” J. Lowe, Y. Seo, M. R. Gagné, ACS Catalysis 2018, 8, 8192-8198.
- “Positional selectivity in the hydrosilylative partial deoxygenation of disaccharides by boron-catalysts” Y. Seo, M. R. Gagné, ACS Catalysis, 2018, 8, 81-85.
- “Homogeneous Catalysis for the Valorization of Cellulosic Biomass: Low-Volume High-Value Components of the Integrated Biorefinery” T. A. Bender, J. A. Dabrowski, M. R. Gagné, Nature Reviews Chemistry 2018, 2, 35-46.
- “Phosphines as Silylium Ion Carriers for Controlled C–O Deoxygenation: Catalyst Speciation and Turnover Mechanisms” A. Gudz, P. Payne, M. R. Gagné, Organometallics, 2017, 36, 4047-4053.
- “Delineating The Multiple Roles of B(C6F5)3 in the Chemoselective Deoxygenation of Unsaturated Polyols” T. A. Bender, J. A. Dabrowski, M. R. Gagné, ACS Cat. 2016, 6, 8399-8403.
- “Diastereoselective B(C6F5)3-Catalyzed Reductive Carbocyclization of Unsaturated Carbohydrates” T. A. Bender, J. A. Dabrowski, H. Zhong, M. R. Gagné, Org. Lett. 2016, 18, 4120-4123.
- “Chemoselective conversion of biologically sourced polyols into chiral synthons” L. A. Adduci, T. A. Bender, J. A. Dabrowski, M. R. Gagné Nature: Chemistry 2015, 7, 576-581.