Chemoselective Quinoline and Isoquinoline Reduction by Energy Transfer Catalysis Enabled Hydrogen Atom Transfer.

(Hetero)arene reduction is one of the key avenues for synthesizing related cyclic alkenes and alkanes. While catalytic hydrogenation and Birch reduction are the two broadly utilized approaches for (hetero)arene reduction across academia and industry over the last century, both methods have encountered significant chemoselectivity challenges. We hereby introduce a highly chemoselective quinoline and isoquinoline reduction protocol operating through selective energy transfer (EnT) catalysis, which enables subsequent hydrogen atom transfer (HAT). The design of this protocol bypasses the conventional metric of reduction reaction, that is, the reductive potential, and instead relies on the triplet energies of the chemical moieties and the kinetic barriers of energy and hydrogen atom transfer events. Many reducing labile functional groups, which were incompatible with previous (hetero)arene reduction reactions, are retained in this reaction. We anticipate that this protocol will trigger the further advancement of chemoselective arene reduction and enable the current arene-rich drug space to escape from flatland.

Rhodium(III)-catalysed redox neutral alkylation of 3-arylbenzo[d]isoxazoles: easy access to substituted succinimides.

A convenient method for the alkylation of 3-arylbenzo[d]isoxazoles with maleimides under redox-neutral conditions has been developed, giving a series of substituted succinimides in up to 99% yield. This transformation is highly selective to give succinimides, and Heck-type products are successfully avoided. This protocol features 100% atom-economy and broad substrate tolerance, and provides a novel strategy for the synthesis of diverse succinimides and an opportunity for the succinylation of protein medication and for pharmacologists to discover first-in-class drugs.

Rhodium-Catalyzed [4 + 2] Cascade Annulation to Easy Access N-Substituted Indenoisoquinolinones.

An efficient approach for the synthesis of N-substituted indenoisoquinolinones via rhodium(III)-catalyzed C-H bond activation/subsequent [4 + 2] cyclization starting from easily available 2-phenyloxazolines and 2-diazo-1,3-indandiones has been developed. A series of indeno[1,2-c]isoquinolinones were obtained in up to 93% yield through C-H functionalization, followed by intramolecular annulation, elimination, and ring-opening in a "one pot manner" under mild reaction conditions. This protocol features excellent atom- and step-economy and provides a novel strategy for the synthesis of N-substituted indenoisoquinolinones and a chance to study their biological activities.