Syntheses and properties of trimethyltetradehydro[15]annulenones and the benzannelated derivatives

Syntheses and properties of dichlorodimethyltetradehydro-trideca-,-pentadeca-, -heptadeca-, and -nonadeca-fulvene, and benzannelated pentadecafulvene derivatives

“…Also, from an examination of the 'H n.m.r. spectra, it was found that the dibenzannelated fulvene (9) exists in the unlikely conformation (9a) and the monobenzannelated fulvene (8) also exists in the conformation (8a) at -30 "C, although the non-benzannelated (4; n = 1) and the monobenzannelated fulvene (7) exist in the conformations indicated. The existence of these unexpected conformations of (8a) and (9a) prompted us to investigate the effect of benzannelation upon the molecular skeleton of dichlorodimethylpentadecafulvene (1 9), and we attempted the preparation of its benzannelated derivatives.…”