S8-mediated cyclotrimerization of 4,5-dihydrobenz[l]acephenanthrylene:: trinaphthodecacyclene (C60H30) isomers and their propensity towards cyclodehydrogenation

It is shown using (high-resolution) mass spectrometry that treatment of 4,5-dihydrobenz[I]acephenanthrylene (2, C20H14) and S-8 in the melt gives the insoluble 532 a.m.u. (C40H20S) and 750 a.m.u. (C60H30) bisbenz[l]acephenanthrothiophenes (4a-c) and, trinaphtho[2,1-b,2,1-m,2,1-x]- (3a) and trinaphtho[2,1-b,2,1-m,1,2-a']decacyclene (3b), respectively (estimated ratio 4a-c/3a-b 20:1), Whereas 3a fits the 'C-60 Schlegel diagram' and might be converted into C-60 (720 a.m.u.) after full cyclodehydrogenation, 3b can only give a curved C60H12/C60H10 (732:730 a.m.u.), MALDI time-of-flight mass spectrometry shows that cyclodehydrogenations of 3a-b down to 732:730 a.m.u. occur; no evidence for C60 formation was found. This is attributed to the preferred formation of 3b, the lack of cyclodehydrogenation selectivity and the occurrence of C-2 extrusions. (C) 1999 Elsevier Science B.V. All rights reserved.