A tandem hexaannulation reaction of benzyllithium involving base-induced cyclodehydrogenation

The reaction of the tribenzo[3.3.3]propellane ketone 1 (triptindan-9-one) w ith benzyllithium/TMEDA affords an efficient one-pot peri annulation of a d ihydronaphthalene across two wings of the propellane framework. The key ste p of this surprising tandem reaction was determined to be a nucleophilic cy clization of (Z)-9-benzylidenetriptindane (4) with concomitant hydride elim ination. The formation of the novel centrotetracyclo[5.5.5.6] framework bea ring a distorted (E)-stilbene unit was confirmed by single-crystal X-ray st ructure analysis.