Dihydrolevoglucosenone as a bio-based catalytic solvent for efficient reductive-transformation of CO2 with amines into formamides and benzothiazoles

Transformation of CO2 as the C1 resource to produce value-added chemicals is of great importance to decrease CO2 emission. In this context, development of green catalytic systems, especially those derived from renewable resources, is highly attractive to make the processes of converting CO2 more sustainable, which has gained significant interest. In this work, cellulose-derived dihydrolevoglucosenone (DLGO, Cyrene™) was employed as a renewable catalytic solvent to convert CO2. DLGO was highly efficient for reductive conversion of CO2 with amines using PhSiH3 as the reductant, and various corresponding formamides could be selectively synthesized. Reaction kinetics analysis suggested that DLGO-based catalytic system possessed a higher reaction rate constant and lower apparent activation energy than both GVL and CH3CN-based catalytic systems. Furthermore, systematic studies revealed that DLGO with high polarity had strong ability to activate the N–H bond in amines and the Si-H bond in PhSiH3 by the solvent effect (i.e., solvation and polarization), thereby making the catalytic system be highly efficient. This developed biomass-based catalytic system could be expanded to synthesize benzothiazoles from the reductive conversion of CO2 with aminothiophenols using PhSiH3 as the reductant. Notably, the DLGO-based system combined CO2 transformation and biomass utilization, affording it possessing more values of practical applications.