Building C(sp 3 )-rich complexity by combining cycloaddition and C-C cross-coupling reactions.

Prized for their ability to rapidly generate chemical complexity by building new ring systems and stereocentres ¹ , cycloaddition reactions have featured in numerous total syntheses ² and are a key component in the education of chemistry students ³ . Similarly, carbon-carbon (C-C) cross-coupling methods are integral to synthesis because of their programmability, modularity and reliability ⁴ . Within the area of drug discovery, an overreliance on cross-coupling has led to a disproportionate representation of flat architectures that are rich in carbon atoms with orbitals hybridized in an sp ² manner ⁵ . Despite the ability of cycloadditions to introduce multiple carbon sp ³ centres in a single step, they are less used ⁶ . This is probably because of their lack of modularity, stemming from the idiosyncratic steric and electronic rules for each specific type of cycloaddition. Here we demonstrate a strategy for combining the optimal features of these two chemical transformations into one simple sequence, to enable the modular, enantioselective, scalable and programmable preparation of useful building blocks, natural products and lead scaffolds for drug discovery.