Visualization of Pathway Usage in an Extended Carbohydrate Conversion Network Reveals the Impact of Solvent Enabled Proton Transfer

Bio-sourced molecules should increasingly contribute to meeting societal demands for energy and chemicals, while reducing net carbon dioxide release and the dependence on fossil resources. Especially oxygenated chemicals can be derived from carbohydrates, and the conversion of carbohydrates in protic and non-protic solvents has attracted considerable interest. Here we probe chemocatalytic carbohydrate conversion in a time-resolved manner using quantitative in situ NMR spectroscopy. A core reaction network in the carbohydrate conversion by Sn(IV) in non-protic solvents is followed by identifying and quantitatively tracking ten chemicals with more than 70 atomic sites. The in situ analysis yields nine rate constants and shows that (co)solvents with labile protons strongly affect tautomerization kinetics and product distributions at an upstream branch point of the reaction network. Solvent enabled tautomerization and the ensuing accumulation of reactive 1,2-dicarbonyl compounds can thus be key factors influencing reaction kinetics and atom economy in carbohydrate conversion.