Non-Pyrolytic Syntheses of Buckybowls:  Corannulene, Cyclopentacorannulene, and a Semibuckminsterfullerene

Corannulene ( 1 ), cyclopentacorannulene ( 2 ), and a C 30 H 12 semibuckminsterfullerene ( 3 ) have been prepared by non-pyrolytic methods employing bromomethyl/dibromomethyl and/or dibromomethyl/dibromomethyl coupling with low-valent titanium or vanadium. Reductive coupling of tetrakis(dibromomethyl)fluoranthene ( 8 ) with vanadium(III) chloride and lithium aluminum hydride affords corannulene in 70−75% yield. Similarly, hexakis(dibromomethyl)fluoranthene ( 13 ) leads to cyclopentacorannulene in 20−30% yield, and dodecabromo(octamethyl)indenofluoranthene ( 6 ) affords semibuckminsterfullerene ( 3 ) in 20% yield.