Broad Scope [4+2] Cycloaddition of o-Carboryne with Pentafulvenes Using 1-Li-2-OTf-o-C2B10H10 as Precursor

o-Carboryne (1,2-dehydro-o-carborane) generated in situ from 1-Li-2-OTf-o-C2B10H10 undergoes an efficient [4 + 2] cycloaddition with pentafulvenes at room temperature to give a series of carboranonorbornenes in good to high isolated yields. This reaction is compatible with many functional groups and has a very broad substrate scope from 6-mono- to 6,6'-disubstituted pentafulvenes and from alkyl to aryl substituents. Further transformations of the resultant [4 + 2] cycloaddition products have been carried out, affording various multi-functionalized o-carboranes.