Reaction of carboryne with styrene and its derivatives

Reaction of carboryne generated from 1-I-2-Li-1,2-C ₂B ₁₀H ₁₀ with styrene and its derivatives has been studied. In addition to [2+2] cycloaddition reaction and/or ene reaction, an extra-annular [4+2] cycloaddition reaction is also observed, depending upon the substituents on the vinyl unit. The resulting [4+2] cycloaddition intermediates are so reactive that they immediately undergo rearomatization via either a formal 1,3-hydrogen rearrangement or dehydrogenation initiated by hydrogen abstraction with carboryne in biradical form, to give 3,4-dihydronaphtho[1,2]-o- carboranes and naphtho[1,2]-o-carboranes, respectively. In sharp contrast to that of benzyne, further additions of carboryne onto the primary cycloadducts are not observed.