Copper-Catalyzed Oxygenative Skeletal Rearrangement of Tetrahydro-β-carbolines Using H O and O as Oxygen Sources.

Herein, we report an unprecedented skeletal rearrangement reaction of tetrahydro-β-carbolines enabled by copper-catalyzed single-electron oxidative oxygenation, in which H O and O act as oxygen sources to generate a unique 2-hydroxyl-3-peroxide indoline intermediate. The synthetic reactivity of 2-hydroxyl-3-peroxide indoline species was demonstrated by a unique multi-step bond cleavage and formation cascade. Using a readily available copper catalyst under open-air conditions, highly important yet synthetically difficult spiro[pyrrolidone-(3,1-benzoxazine)] products were obtained in a single operation. The synthetic utility of this methodology is demonstrated by the efficient synthesis of the natural products donaxanine and chimonamidine, as well as the 3-hydroxyl-pyrroloindoline scaffold, in just one or two steps.