Nickel-Catalyzed Reaction of Norbornene with Two Alkynes

Significance

The authors report the first example of a three-component C-H activation reaction of norbornene with two alkynes leading to 1,5-enynes. The process is efficiently mediated by the Ni(cod)₂/phosphine catalyst with high regio- and stereoselectivities. If two different alkynes were employed (eq. 1), the corresponding products were obtained with moderate to good yields and high regioselectivities. The protocol was also carried out using only terminal silylacetylene as an alkyne (eq. 2); a broader scope of the alkene counterpart was tolerated. Unfortunately, the substrate scope is limited to [2.2.1]bicyclic systems. The utility of this method would be significantly broader if it could be generally applied to cyclic olefins.