Syntheses of an isoannelated annulene, a bisdehydro[14]annuleno[c]furan and bisdehydro[14]annulene derivatives

✍ Scribed by Hajime Ebe; Tsutomu Nakagawa; Masahiko Iyoda; Masazumi Nakagawa

• Publisher: Elsevier Science
• Year: 1981
• Tongue: French
• Weight: 257 KB
• Volume: 22
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(01)82978-6

✦ Synopsis

A bisdehydro[l4]annuleno[c]furan, an isoannelated diatropic annulene, has been synthesized. Cyclic glycol, a precursor of the annuleno[c]furan, could be converted into bisdehydro[l4]annulene derivatives under mild acidic conditions. We have already prepared a series of annelated [4n+2]annulenes fused with naphthalene or benzene and clarified the effect of annelation on n-electron delocalization of the annulene 1) ring . Recently we have prepared [4n+2]annuleno[4n'+2]annulenes (l) consisting of two same or different size diamagnetic 'acetylene-cumulene' dehydroannulenes, and their NMR properties strongly suggest that they are fused systems of two diatropic moieties'). With the purpose to get further insight into the nature of ring current induced in annulenoannulene system, we have intended to prepare ortho-fused annulenoannulenes (5) consisting of two 'acetylene-cumulene' dehydroannulenes. A bisdehydro[14]annuleno[c]furan ($), a 14aelectron analogue of isobenzofuran , seemed to be a key substance for the preparation of p. In this paper, we wish to report the synthesis of bisdehydro[14]annuleno[c]furan (2) and the formation of bisdehydroCl4lannulene derivatives (,$, %) from the cyclic glycol, the precursor of 2. 1 a, m=n=l; b, m=n=2 , m=l,n=2; d, m=l,n=3 III II 3 4, R=Me; _~,R=Ac The synthesis of the bisdehydro[14]annuleno[c]furan (4) was carried out by the reaction sequence outlined in Scheme 1. 3-Hydroxymethylfuran-4-carboxaldehyde (,!J,)3' was converted into tetrahydropyranyl ether (x, colorless oil, bp 89-90°C / 1.0x10-4mmHg, 82%). The Wittig-Horner reaction of l with LiCCl, -P(O)(OEt)z in THF / ether (2:3) gave gem-dichloroalkene (2, pale yellow oil, bp 102-106°C / 7x10-5mmHg, 74%)4).