Benzimidazole is a commonly used nitrogen heterocycle in U.S. FDA approved drugs; therefore, a direct and sustainable approach that limits chemical waste for the synthesis of substituted benzimidazoles is appealing. We have developed an electrosynthetic approach that is able to synthesize a variety of 1H-substitubed benzimidazoles while concurrently producing H2, without a transition-metal catalyst or added bases. Furthermore, the procedure works efficiently with only simple carbon electrodes, thus avoiding commonly employed platinum and gold electrodes. Desired products were achieved with up to 88% yield, illustrating the range and possible sustainability of this approach.
The lignocellulose-to-ethanol processes has made use of cellulose and hemicellulose, however leaves the lignin component behind as waste. Typically, lignin is utilized as a low-grade energy source through combustion without further upgrading the energy content, however, the chemical structure of lignin displays potential to be used as a viable chemical feedstock through depolymerization to monomeric units. Selective deoxygenation of monomeric units from lignin will not only increase energy density of the monomers, but could also lead to the development of new chemical feedstocks. This removal of oxygen can be examined more closely through the use of compounds that model the monomeric units of lignin. Aromatic compounds possessing alcohols or other oxygenated substituents are widely available, thus allowing the testing of selective hydrodeoxygenation. The model compounds chosen for this study, benzyl alcohol, benzaldehyde, and benzophenone, contain three of the common structural motifs found in depolymerized lignin. The molecular, homogeneous catalysts [Pd(tpy)Cl]Cl, where tpy is 2,2′:6′,2′′- terpyridine, exhibits excellent catalytic activity with the complete selectivity towards hydrodeoxygenation.