Pure and Applied Chemistry

Abstract: Benzannulated enyne-allenes bearing an aryl substituent at both the alkynyl and allenyl termini are excellent precursors of 5-aryl-11H-benzo[b]fluorenyl derivatives having the carbon frameworks of fullerene fragments. The mildness of the reaction conditions and the availability of several synthetic methods for benzannulated enyne-allenes allow the design of new synthetic pathways leading to bowl- and basket-shaped fullerene fragments. Specifically, a bowl-shaped C₂₈H₁₈ hydrocarbon bearing a 27-carbon framework of C₆₀ and a basket-shaped C₅₆H₄₀ hydrocarbon bearing a 54-carbon framework of C₆₀ were synthesized. The interior 30-carbon core of the C₅₆H₄₀ hydrocarbon can be regarded as a partially hydrogenated [5,5]circulene, a C₃₀H₁₂ semibuckminsterfullerene. In addition, a basket-shaped C₅₆H₃₈ hydrocarbon was also constructed to serve as a precursor toward an end-cap template for (6,6) carbon nanotubes.