Copper-Catalyzed Selective Oxidative Cross-Coupling of Tryptophols and Tryptamines To Access Heterocyclic 3a,3a'-Bisindolines

Copper-Catalyzed Tunable Oxygenative Rearrangement of Tetrahydrocarbazoles

Herein, we report a general copper-catalyzed method for the tunable oxygenative rearrangement of tetrahydrocarbazoles to cyclopentyl-bearing spiroindolin-2-ones and spiroindolin-3-ones. The method demonstrates excellent chemoselectivity, regioselectivity, and product control simply by using the H2O and O2 as oxygen source, respectively. This open-flask method is safe and simple to operate, and no other chemical oxidants are required. Besides, inspired from the unique pathway of 1, 2-migration rearrangement, a highly controllable hydroxylation of indoles for the construction of C3a-hydroxyl iminium indolines was also developed. Mechanistic experiments suggest that a single-electron transfer-induced oxidation process is responsible for the tunable selectivity control.

Copper/Iodine Co-catalyzed Oxygenative Transannulation of Tryptamines Enables Direct Synthesis of Donaxaridine and Its Derivatives

We report a general copper/iodine co-catalyzed oxygenative transannulation strategy using readily available tryptamines. Molecular oxygen and water are used as oxygen sources and provide direct access to the donaxaridine scaffold and its derivatives. This methodology is applied to the efficient synthesis of the natural products donaxaridine, chimonamidine, donaxanine, donaxarine, and aline in just one or two steps. The tryptamines, albeit with oxy-sensitive dialkyl N-H groups, are selectively oxidized through a single-electron transfer dioxygenation process.

Copper-Catalyzed Aerobic Selective Oxidation of Tetrahydrocarbolines

We report a safe and convenient open-flask copper-catalyzed selective oxidation/functionalization methodology for tetrahydrocarbolines and tetrahydro-β-carbolines that employs atmospheric O₂ as the terminal oxidant. The system is applicable to oxidative rearrangement of tetrahydro-β-carbolines, tetrahydrocarboline oxidation to α-alkoxy carbazoles and spirooxindoles, and Witkop oxidation. Mechanistic experiments indicated that a single-electron oxidation process is responsible for the tunable selectivity control. This copper-catalysis protocol represents a significant advance in the field of indole oxidation.

Copper-catalyzed cascade reaction of tryptamines with diazo compounds to access hexahydropyrroloindoline derivatives

A Cu-catalyzed cyclopropanation/ring-opening/iminium cyclization of tryptamine derivatives with donor–acceptor diazo compounds is developed to furnish pyrroloindolines, creating three consecutive stereogenic centers.