Catalytic reductive [4 + 1]-cycloadditions of vinylidenes and dienes.

Zhou, You-Yun; Uyeda, Christopher · Science · 2019

basic_science · Level V

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Abstract

Cycloaddition reactions provide direct and convergent routes to cycloalkanes, making them valuable targets for the development of synthetic methods. Whereas six-membered rings are readily accessible from Diels-Alder reactions, cycloadditions that generate five-membered rings are comparatively limited in scope. Here, we report that dinickel complexes catalyze [4 + 1]-cycloaddition reactions of 1,3-dienes. The C<sub>1</sub> partner is a vinylidene equivalent generated from the reductive activation of a 1,1-dichloroalkene in the presence of stoichiometric zinc. Intermolecular and intramolecular variants of the reaction are described, and high levels of asymmetric induction are achieved in the intramolecular cycloadditions using a <i>C</i> <sub>2</sub>-symmetric chiral ligand that stabilizes a metal-metal bond.