Synergistic catalysis: cobalt-catalyzed cascade reaction for the oxidative cleavage of olefins to access esters.

An efficient strategy for the oxidative cleavage of CC bonds in olefins to form esters with one or multiple carbon atoms less over heterogeneous cobalt/nitrogen-doped carbon catalyst with dioxygen as the oxidant was described. The protocol features a wide substrate range including the challenging inactive aliphatic and long-chain alkyl aryl olefins. The reactivity of the catalyst did not decrease after reused for seven times. Characterization and control experiments reveal that synergistic effects between the metallic Co nanoparticles and Co-Nx sites provide access to the excellent catalytic activity.

Metal-Free Nitrogen-Doped Mesoporous Carbons for the Mild and Selective Synthesis of Pyrroles from Nitroarenes via Cascade Reaction.

The cascade synthesis of pyrroles from nitroarenes is an attractive alternative strategy. However, metal catalysts and relatively high temperatures cover the existing reported catalytic systems for this strategy. The development of nonmetallic heterogeneous catalytic systems for the one-pot synthesis of pyrrole from nitroarenes under mild conditions is both worthwhile and challenging. Herein, we describe an exceptionally efficient method for the synthesis of N-substituted pyrroles by the reductive coupling of nitroarenes and diketones over heterogeneous metal-free catalysts under mild conditions. Nonmetallic NC-X catalysts with high activity were prepared from the pyrolysis of well-defined ligands via simple sacrificing hard template methods. Hydrazine hydrate, formic acid, and molecular hydrogen can all be used as reducing agents in the hydrogenation/Paal-Knorr reaction sequence to efficiently synthesize various N-substituted pyrroles, including drugs and bioactive molecules. The catalytic system was featured with good tolerance to sensitive functional groups and no side reactions such as dehalogenation and aromatics hydrogenation. Hammett correlation studies have shown that the electron-donating substituents are beneficial for the one-pot synthesis of N-substituted pyrroles. The results established that the outstanding performance of the catalyst is mainly attributed to the contribution of graphitic N in the catalyst as well as the promotion effect of the mesoporous structure on the reaction.

Copper/Nitroxyl-Catalyzed Synthesis of Pyrroles by Oxidative Coupling of Diols and Primary Amines at Room Temperature.

The Cu/ABNO-catalyzed aerobic oxidative coupling of diols and primary amines to access N-substituted pyrroles is highlighted (ABNO = 9-azabicyclo[3.3.1]nonane N-oxyl). The reaction proceeds at room temperature with an O2 balloon as the oxidant using commercially available materials as the substrates and catalysts. The catalyst system is characterized by a broad range of substrates and a good tolerance to sensitive functional groups. The gram-scale experiment proves this system's practicability.