Copper-Catalyzed Cyclization and Alkene Transposition Cascade Enables a Modular Synthesis of Complex Spirocyclic Ethers.

Complexity-generating reactions that access three-dimensional products from simple starting materials offer substantial value for drug discovery. While oxygen-containing heterocycles frequently feature unique, nonaromatic architectures such as spirocyclic rings, exploration of these chemical spaces is limited by conventional synthetic approaches. Herein, we report a copper-catalyzed annulation and alkene transposition cascade reaction that enables a modular preparation of complex, spirocyclic ethers from readily available alkenol substrates via a copper-catalyzed annulation and transannular 1,5-hydrogen atom transfer-mediated C-H functionalization. Our transformation displays a broad substrate scope, shows excellent heteroatom compatibility, and readily constructs spirocycles of varying ring sizes. The wider synthetic utility of this method is highlighted by numerous product diversifications and a short synthesis of the all-carbon framework of spirotenuipesine A. We anticipate that this transformation can significantly streamline access to a privileged class of three-dimensional oxygen-containing heterocycles and will find broad application in natural product synthesis.