The transfer hydrogenation of CO2 from glycerol to afford formic and lactic acid is a highly attractive path to valorizing two waste streams and is a significantly more thermodynamically favorable process than direct CO2 hydrogenation. We report the first homogeneous catalyst for this transformation consisting of a water-soluble Ru N-heterocyclic carbene complex. The catalyst affords lactic and formic acid selectively in the presence of a base at temperatures between 150 and 225 °C. Carbonate salts can also be utilized in place of CO2, affording the same products at higher rates.

Voutchkova -Kostal, Adelina (2018): Acceptorless amine dehydrogenation and transamination using Pd-doped layered double hydroxides. ChemRxiv. Preprint.The synthesis, characterization, and activity of Pd-doped layered double hydroxides (Pd-LDHs) for for acceptorless amine dehydrogenation is reported. These multifunctional catalysts comprise Brønsted basic and Lewis acidic surface sites that stabilize Pd species in 0, 2+, and 4+ oxidation states. Pd speciation and corresponding cataytic performance is a strong function of metal loading. Excellent activity is observed for the oxidative transamination of primary amines and acceptorless dehydrogenation of secondary amines to secondary imines using a low Pd loading (0.5 mol%), without the need for oxidants. N-heterocycles, such as indoline, 1,2,3,4-tetrahydroquinoline, and piperidine, are dehydrogenated to the corresponding aromatics with high yields. The relative yields of secondary imines are proportional to the calculated free energy of reaction, while yields for oxidative amination correlate with the electrophilicity of primary imine intermediates.Reversible amine dehydrogenation and imine hydrogenation determine the relative imine:amine selectivity.Poisoning tests evidence that Pd-LDHs operate heterogeneously, with negligible metal leaching; catalysts can be regenerated by acid dissolution and re-precipitation. a The synthesis, characterization, and activity of Pd-doped layered double hydroxides (Pd-LDHs) for for acceptorless amine dehydrogenation is reported. These multifunctional catalysts comprise Brønsted basic and Lewis acidic surface sites that stabilize Pd species in 0, 2+, and 4+ oxidation states. Pd speciation and corresponding cataytic performance is a strong function of metal loading. Excellent activity is observed for the oxidative transamination of primary amines and acceptorless dehydrogenation of secondary amines to secondary imines using a low Pd loading (0.5 mol%), without the need for oxidants. N-heterocycles, such as indoline, 1,2,3,4-tetrahydroquinoline, and piperidine, are dehydrogenated to the corresponding aromatics with high yields. The relative yields of secondary imines are proportional to the calculated free energy of reaction, while yields for oxidative amination correlate with the electrophilicity of primary imine intermediates. Reversible amine dehydrogenation and imine hydrogenation determine the relative imine:amine selectivity. Poisoning tests evidence that Pd-LDHs operate heterogeneously, with negligible metal leaching; catalysts can be regenerated by acid dissolution and re-precipitation.

The transfer hydrogenation of CO2 and carbonates from biomass-derived alcohols, such as glycerol, to afford formic and lactic acid is a highly attractive path to valorizing two waste streams, and...

Scheme1.Decarbonylation strategy for converting lignocellulose to platform chemicals HMF,furfural, furfuryl alcohol, and furan.[a] Dr.

New atom-economical alternatives to Wittig chemistry are needed construct olefins from carbonyl complexes, but none have been developed to-date. Here we report an atom-economical olefination of carbonyls via aldol-decarbonylative coupling of aldehydes using robust and recyclable supported Pd catalysts, producing only CO and H2O as waste. The reaction accommodates homocoupling of aldehydes with an a a-methylene groups, as well as heterocoupling. Computations provide insight into the selectivity of the reaction. The tandem aldol-decarbonylation reaction opens the door to exploration of new carbonyl reactivity to construct olefins. R 1 -CO

Multistep H2-free upgrading of alcohols to liquid hydrocarbons is highly desirable for producing drop-in fuel substitutes, but the limited reports of this process for select substrates require multiple catalysts and bases, resulting in limited applicability. Direct conversion processes that rely on multifunctional catalysts and do not require base are yet to be reported. Here we describe such a Pd-catalyzed deoxygenative coupling of heptanol with heterogeneous catalysts composed of Pd immobilized on acid–base supports, which actively participate in the reaction cascade. The supports include primarily basic MgO, acidic γ-Al2O3, and Mg–Al hydrotalcite (HT), with a combination of Lewis acidic and basic sites. Pd–HTs with 1% and 5 wt % Pd loading afforded the highest overall activity in the multistep cascade, yielding 30% hydrocarbons (tridecene 6-E-tridecene and tridecane) from a neat reaction with heptanol with 0.2 mol % Pd loading. Heterogeneity tests suggest that Pd–HT is operationally heterogeneous. The impact of support selection on the activity and selectivity offers insights into the design principles for next-generation catalysts for this process and related transformations.

<p>Here we report the synthesis, characterization and activity of tunable Pd-doped hydrotalcites (Pd-HTs) for the decarbonylation of furfural, hydroxymethylfurfural (HMF), aromatic and aliphatic aldehydes under microwave conditions. The decarbonylation activity reported is a notable improvement over prior heterogeneous catalysts for this process. Furfural decarbonylation is optimized in a benign solvent compatible with biomass processing - ethanol, under relatively mild conditions and short reaction times. HMF selectively affords excellent yields of furfuryl alcohol with no humin formation, but longer reaction can also afford furan via tandem alcohol dehydrogenation and decarbonylation. Yields of substituted benzaldehydes are related to calculated Mulliken charge of the carbonyl carbon. The activity and selectivity differences can be traced to loading-dependent differences in Pd speciation on the catalysts. Poisoning studies show inverse correlation between Pd loading and metal leaching: Pd-HTs with lowest Pd loading, which consist of highly dispersed and oxidized Pd species, operate heterogeneously with negligible metal leaching. Recycling experiments are consistent with this trend, offering potential for further optimization to improve robustness.</p>

<p>Here we report the synthesis, characterization and activity of tunable Pd-doped hydrotalcites (Pd-HTs) for the decarbonylation of furfural, hydroxymethylfurfural (HMF), aromatic and aliphatic aldehydes under microwave conditions. The decarbonylation activity reported is a notable improvement over prior heterogeneous catalysts for this process. Furfural decarbonylation is optimized in a benign solvent compatible with biomass processing - ethanol, under relatively mild conditions and short reaction times. HMF selectively affords excellent yields of furfuryl alcohol with no humin formation, but longer reaction can also afford furan via tandem alcohol dehydrogenation and decarbonylation. Yields of substituted benzaldehydes are related to calculated Mulliken charge of the carbonyl carbon. The activity and selectivity differences can be traced to loading-dependent differences in Pd speciation on the catalysts. Poisoning studies show inverse correlation between Pd loading and metal leaching: Pd-HTs with lowest Pd loading, which consist of highly dispersed and oxidized Pd species, operate heterogeneously with negligible metal leaching. Recycling experiments are consistent with this trend, offering potential for further optimization to improve robustness.</p>