Intercepting fleeting cyclic allenes with asymmetric nickel catalysis.

Strained cyclic organic molecules, such as arynes, cyclic alkynes, and cyclic allenes, have intrigued chemists for over a century1. The high degree of ring strain (30–50 kcal/mol)2,3 that characterizes these transient intermediates imparts high reactivity in many reactions, including cycloadditions and nucleophilic trappings, often generating structurally complex products4. Although strategies to control absolute stereochemistry in these reactions have been reported using stoichiometric chiral reagents5,6, catalytic asymmetric reactions of strained cyclic intermediates to generate enantioenriched products have remained elusive. Here we report the interception of racemic cyclic allene intermediates in a catalytic asymmetric reaction and provide evidence for two distinct mechanisms to control absolute stereochemistry in such transformations. Computational studies implicate a catalytic mechanism involving initial kinetic differentiation of the cyclic allene enantiomers through stereoselective olefin insertion, loss of the resultant stereochemical information, and subsequent introduction of absolute stereochemistry through desymmetrization of an intermediate π-allylnickel complex. These results demonstrate new reactivity available to cyclic allenes beyond the traditional cycloadditions and nucleophilic trappings previously reported, thus expanding the products accessible from this class of intermediates. Additionally, our computational studies elucidate two potential strategies for stereocontrol in reactions of cyclic allenes. Combined, these results lay the foundation for the development of catalytic asymmetric reactions involving these classically avoided strained intermediates.