Noucti NN, Alexanian EJ * The University of North Carolina at Chapel Hill, USA
Stereoselective Nickel-Catalyzed [2+2] Cycloadditions of Ene-Allenes.
Angew. Chem. Int. Ed. 2015;
54: 5447-5450
Key words
nickel - ene-allenes - [2+2] cycloaddition
Significance
The [2+2] cycloaddition of ene-allenes is a powerful methodology in the construction
of fused cyclobutanes. However, one of the challenges of known protocols is the limited
substrate scope, tolerating only styrene or diene π-components. Alexanian and Noucti
demonstrate the utility of nickel catalysis in a stereoselective [2+2]-cycloaddition
to generate diverse carbocyclic frameworks A.
Comment
It is noteworthy to point out the effectiveness of this protocol to cyclize terminal
allenes which are not tolerated in other known methods. Moreover, an interesting observation
was discovered where methyl substitution at R2 changes the [2+2] cycloaddition from the proximal to the distal π-bond of the allene,
generating the bicyclo[4.2.2] scaffold B instead.
