Cycloaromatization of a non-conjugated polyenyne system: Synthesis of 5H-benzo[d]fluoreno[3,2-b]pyrans via diradicals generated from 1-[2-{4-(2-alkoxymethylphenyl)butan-1,3-diynyl}]phenylpentan-2,4-diyn-1-ols and trapping evidence for the 1,2-didehydrobenzene diradical

✍ Scribed by Kazuhiro Miyawaki; Riho Suzuki; Tomikazu Kawano; Ikuo Ueda

• Book ID: 104257147
• Publisher: Elsevier Science
• Year: 1997
• Tongue: French
• Weight: 234 KB
• Volume: 38
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(97)00785-5

✦ Synopsis

Non-conjugated tetraynes 1 undergo thennal intmmolecul~ cyclization to non-benzenoiddiradicals (23) followed by radical cycloaromatization at 25 ~C to provide 7-dehydro-5H-benzo[d]fluoreno[3,2-b]pyran monoradical (2 4) and alkyl radicals (2 5). Hydrogen abstraction of 2 4 gives 5H-benzo[d] fluoreno[3,2-b]pyrans (3) which are converted to 4 by reaction with 2 5. On the other hand, 2 gives5H-fluorenol(5),indicatingtheformationofl,2-didehy~ diradical intermediates (28 and 29). These radicals are trapped as the corresponding Diels-Alder-type products by reaction with an aromatic diene, anthracene. O 1997 Elsevier Science Ltd.