Alkynyl hydrazones are synthesized conveniently from 2-oxo-3-butynoates and hydrazine by suppressing the susceptible formation of pyrazoles. The resultant hydrazones are transformed into alkynyl diazoacetates under metal-free and mild oxidative conditions in excellent yields. Further, the alkynyl cyclopropane and propargyl silane carboxylates are synthesized in good yields by developing an unprecedented copper-catalyzed alkynyl carbene transfer reaction.
Our dependence on finite fossil fuels and the insecure energy supply chains have stimulated intensive research for sustainable technologies. Upcycling glycerol, produced from biomass fermentation and as a biodiesel formation byproduct, can substantially contribute in circular carbon economy. Here, we report glycerol’s solvent-free and room-temperature conversion to high-added-value chemicals via a reusable graphene catalyst (G-ASA), functionalized with a natural amino acid (taurine). Theoretical studies unveil that the superior performance of the catalyst (surpassing even homogeneous, industrial catalysts) is associated with the dual role of the covalently linked taurine, boosting the catalyst’s acidity and affinity for the reactants. Unlike previous catalysts, G-ASA exhibits excellent activity (7508 mmol g−1 h−1) and selectivity (99.9%) for glycerol conversion to solketal, an additive for improving fuels’ quality and a precursor of commodity and fine chemicals. Notably, the catalyst is also particularly active in converting oils to biodiesel, demonstrating its general applicability.
Enantioselective organocatalytic protocols for the functionalization of electron-deficient internal alkynes and enynes are reviewed. This review focuses on the applicability of activated conjugated π-systems in asymmetric synthesis for providing diversified chiral entities under metal-free reaction conditions. Various organocatalytic strategies with different catalytic modes are demonstrated.
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