Novel Open-Cage Fullerenes Having a 12-Membered-Ring Orifice: Removal of the Organic Addends from the Rim of the Orifice Georgios C. Vougioukalakis, ² Kosmas Prassides,* ,‡ and Michael Orfanopoulos* ,² Department of Chemistry, UniVersity of Crete, 71409 Iraklion, Greece, and Department of Chemistry, UniVersity of Sussex, Brighton BN1 9QJ, UK orfanop@chemistry.uoc.gr Received January 27, 2004 ABSTRACT Two novel open-cage fullerene derivatives bearing a 12-membered-ring orifice on the fullerene cage have been isolated. Removal of the N-MEM protective group leads to the first open-cage [60]fullerene derivative without organic addends on the rim of the orifice. N-MEM-ketolactam 1 (Scheme 1), the first reported open- cage fullerene derivative, was isolated in 1995 by Wudl and co-workers. 1 Since then, several synthetic procedures toward the formation of an orifice in the fullerene shell have been developed. 2-6 Opened species, bearing sufficiently large apertures to incorporate atoms, molecules or ions such as He, Ne, H 2 ,N 2 , or Li + , are important members in the fullerene family because of their potential use in the production of endohedral fullerene derivatives. Endohedral fullerenes are currently being formed by utilizing the evaporation of graphite-metal composites, high-temperature and high-pressure conditions, ion implantation, or high- energy plasma insertions into pure fullerenes. 7-10 The chemi- cal creation and then closure of the opening, following the encapsulation of the desired species within the fullerene cage, known as the “molecular surgery” approach, has been proposed as an alternative route to the synthesis of endohe- dral fullerenes. This has proven to be possible quite recently by the gas-phase generation of H 2 @C 60 during MALDI-TOF mass spectrometry experiments of an open-cage fullerene derivative. 11 Following the work of Wudl, 1 Rubin and co-workers prepared an open-cage bislactam [60]fullerene derivative with ² University of Crete. ‡ University of Sussex. (1) Hummelen, J. C.; Prato, M.; Wudl, F. J. Am. Chem. Soc. 1995, 117, 7003-7004. (2) Schick, G.; Jarrosson, T.; Rubin, Y. Angew. Chem., Int. Ed. 1999, 38, 2360-2363. (3) Murata, Y.; Murata, M.; Komatsu, K. Chem. Eur. J. 2003, 9, 1600- 1609. (4) Iwamatsu, S.-I.; Ono, F.; Murata, S. Chem. Commun. 2003, 1268- 1269. (5) Murata, Y.; Murata, M.; Komatsu, K. J. Org. Chem. 2001, 66, 8187- 8191. (6) Inoue, H.; Yamaguchi, H.; Iwamatsu, S.-I.; Uozaki, T.; Suzuki, T.; Akasaka, T.; Nagase, S.; Murata, S. Tetrahedron Lett. 2001, 42, 895-897. (7) Shinohara, H. Rep. Prog. Phys. 2000, 63, 843-892. Scheme 1 ORGANIC LETTERS 2004 Vol. 6, No. 8 1245-1247 10.1021/ol049843b CCC: $27.50 © 2004 American Chemical Society Published on Web 03/13/2004