Construction of Fused Tetrahydroquinolines by Catalytic Hydride-Transfer-Initiated Tandem Functionalization of Quinolines.

Herein, we present a new annulation reaction of quinolinium salts with indoles and paraformaldehyde, which enables syn-diastereoselective construction of a vast range of fused tetrahydroquinolines via ruthenium-catalyzed hydride-transfer-initiated tandem functionalization of the quinoline skeleton. The developed transformation proceeds with mild reaction conditions, good substrate and functional group compatibility, readily available feedstocks, and operational simplicity.

Practical iridium-catalyzed direct α-arylation of N-heteroarenes with (hetero)arylboronic acids by H2O-mediated H2 evolution.

Despite the widespread applications of 2-(hetero)aryl N-heteroarenes in numerous fields of science and technology, universal access to such compounds is hampered due to the lack of a general method for their synthesis. Herein, by a H2O-mediated H2-evolution cross-coupling strategy, we report an iridium(III)-catalyzed facile method to direct α-arylation of N-heteroarenes with both aryl and heteroaryl boronic acids, proceeding with broad substrate scope and excellent functional compatibility, oxidant and reductant-free conditions, operational simplicity, easy scalability, and no need for prefunctionalization of N-heteroarenes. This method is applicable for structural modification of biomedical molecules, and offers a practical route for direct access to 2-(hetero)aryl N-heteroarenes, a class of potential cyclometalated C^N ligands and N^N bidentate ligands that are difficult to prepare with the existing α-C-H arylation methods, thus filling an important gap in the capabilities of synthetic organic chemistry.

Ruthenium-Catalyzed Hydrogen Evolution o-Aminoalkylation of Phenols with Cyclic Amines.

Herein, we present a ruthenium-catalyzed new hydrogen evolution ortho-aminoalkylation of phenolic derivatives with cyclic amines as the coupling agents. The developed cross-coupling reaction offers a practical platform for direct access to a variety of functionalized phenols with the features of good substrate and functional group compatibility, readily available catalyst system and feedstocks, no need for additional sacrificial oxidants, and high atom efficiency.

Synthesis of Diverse Functionalized Quinoxalines by Oxidative Tandem Dual C-H Amination of Tetrahydroquinoxalines with Amines.

The tandem dual C-H amination of tetrahydroquinoxalines with free amines under aerobic copper catalysis conditions has been demonstrated. The synthetic protocol proceeds with good substrate and functional group compatibility, mild reaction conditions, short reaction time, the use of the naturally abundant [Cu]/O2 catalyst system, excellent chemoselectivity and synthetic efficiency, and with no need for the pre-installation of specific aminating agents, which offers a practical platform for the rapid and diverse synthesis of diaminoquinoxalines. Moreover, this work has shown the potential of single-electron-oxidation-induced C-H functionalization of N-heterocycles, and its application in the development of optoelectronic materials.