Various 3,3′-methylenebis azulenes were prepared in high yields upon treatment of 1-substituted azulenes with a solution of 0.1–0.2 wt% paraformaldehyde in glacial acetic acid at 25°C for 1 h. Thus, 1-methyl-, 1-isopropyl-, 1,5-diisopropylazulene, guaiazulene, and methyl 2-hydroxy-1-azulenecarboxylate readily provided the corresponding 3,3′-methylenebisazulenes, respectively. Acetic acid which had been refluxed with 5 wt% KMnO4 for 2 h and then distilled according to a purification method was found to contain 0.1–0.2 wt% formaldehyde and exert the same 3,3′-methylenebisazulene formation. 3,3′-Dideuteriomethyl-enebis(guaiazulene) was obtained by employing the similar distillate from acetic acid-d4.
Autoxidation of the title azulenes at 100 °C in HMPA or DMF afforded a wide variety of products: Namely, the oxidation products of the side-chains, 1-substitutedazulenes, 1H-inden-1-ols, naphthoquinones, benzenoids, and dimeric and trimeric compounds, with or without rearrangements. 1H NMR (200-MHz) parameters of various azulene derivatives are given for comparative study. Possible reaction pathways for the
在 HMPA 或 DMF 中于 100 °C 自动氧化标题甘菊烯可提供多种产物:即,侧链的氧化产物、1-取代的甘菊烯、1H-inden-1-ols、萘醌、苯类和二聚体和三聚化合物,有或没有重排。给出了各种薁衍生物的 1 H NMR (200-MHz) 参数用于比较研究。与先前对愈创甘油醚和 4,6,8-trimethylazulene 的研究结果进行比较,讨论了形成这些产物的可能反应途径。