Formation and Rearrangement of a Congested Spiropentane from the Trapping of Dibenzonorcarynyliden(e/oid) by Phencyclone

The low-temperature treatment of 1,1-dibromo-1a,9b-cyclopropa[l]phenanthrene with butyllithium appeared to produce dibenzonorcarynyliden(e/oid) which could be intercepted with phencyclone to produce a hindered spiropentane. The spiropentane readily rearranges, thermally and photochemically, into a triphenylene phenol derivative. The spiropentane and its rearrangement product were characterized by X-ray crystallography.