Nengchao Luo

Acid promoted C–C bond oxidative cleavage of β-O-4 and β-1 lignin models to esters over a copper catalyst

Depolymerisation of lignin to aromatics is a challenging task. We herein report that a Cu(OAc)2/BF3·OEt2 catalyst is effective in simultaneously cleaving C–C bonds in β-1 and β-O-4 ketones, yielding esters and phenols. In-depth studies show that C–H bond activation is the rate determining step for C–C bond cleavage. BF3·OEt2 promotes the reaction via activating the β-C–H bond. This study offers the potential to obtain aromatic esters from lignin.

Generation and Confinement of Long-lived N-oxyl Radical and its Photocatalysis

Generation of controllable carbon radical under the assistance of N-oxyl radical is an efficient method for the activation of C-H bonds in hydrocarbons. We herein report that irradiation of α-Fe2O3 and N-hydroxyphthalimide (NHPI) under 455 nm light generates phthalimide-N-oxyl radical (PINO*), which after being formed by oxidation with holes, is confined on α-Fe2O3 surface. The half-life time of the confined radical reaches 22 s as measured by in situ electron paramagnetic resonance (EPR) after the light being turned off. This allows the long-lived N-oxyl radical to abstract the H from C-H bond to form a carbon radical that reacts with molecular oxygen to form R3C-OO· species, decomposition of which leads to oxygenated products.

Photocatalytic coupling of amines to imidazoles using a Mo–ZnIn2S4 catalyst

Substituted imidazoles are traditionally synthesized by co-condensation of multiple feedstocks. Herein, we report a new route for the synthesis of substituted imidazoles via photocyclization of readily available amines at room temperature. The reaction is achieved by the visible-light-induced C–C/C–N bond coupling and subsequent dehydrogenation reaction over Mo–ZnIn2S4 as a heterogeneous photocatalyst. A wide range of amines were converted into the corresponding tri- and tetra-substituted imidazoles with up to 96% total yields. The simplicity, high efficiency and mild condition merits of this new reaction will enable it to be useful in synthetic transformations.