Direct synthesis of 2-arylazulenes by [8+2] cycloaddition of 2<i>H</i>-cyclohepta[<i>b</i>]furan-2-ones with silyl enol ethers
作者:Taku Shoji、Shuhei Sugiyama、Yoshiaki Kobayashi、Akari Yamazaki、Yukino Ariga、Ryuzi Katoh、Hiroki Wakui、Masafumi Yasunami、Shunji Ito
DOI:10.1039/c9cc09376a
日期:——
We developed a procedure for the direct synthesis of 2-arylazulenes, which were obtained in moderate to excellent yields, by [8+2] cycloaddition of 2H-cyclohepta[b]furan-2-ones with aryl-substituted silylenolethers. The structures of some 2-arylazulenes were clarified by single-crystal X-ray analysis. The 2-phenylazulene derivatives obtained by this study showed noticeable fluorescence in acidic
example of directed C–H activation for azulene is reported. A variety of 2-arylazulenes are obtainable exclusively from 1-azulene carboxylicacids, with yields of up to 82%. Some heteroaryl groups such as pyridine and thiophene are also tolerated in the reaction. The efficacy of the reaction is found to be highly dependent on the conditions, with a phosphate base and a bulky carboxylicacid being key
First synthesis of 1-(indol-2-yl)azulenes by the Vilsmeier–Haack type arylation with triflic anhydride as an activating reagent
作者:Taku Shoji、Yuta Inoue、Shunji Ito
DOI:10.1016/j.tetlet.2012.01.044
日期:2012.3
Azulene derivatives reacted with 2-indolinones in the presence of triflic anhydride (Tf2O) to afford 1-(indol-2-yl)azulenes in good yields. In the cases of the reaction of 6-tert-butyl-1-(methylthio)azulene (11) and 1-(1,4-dihydropyridin-4-yl)azulene 14, 1,1′-biazulene derivative 24 and 1-(indol-2-yl)azulene (2) were obtained under the similar reaction conditions, respectively, instead of the presumed
ring closure at the 8-position. 2-(Phenylsulfanyl)-1-azulenyl p-tolyl sulfone (2b) suffered from desulfonylation to form 2-phenylsulfanylazulene (4). The Suzuki couplingreaction of 2-iodo-1-azulenyl p-tolyl sulfone (2d) with arylboronicacids followed by desulfonylation efficiently gave 2-arylazulenes 10.
3-difluoroazulenes were synthesized for the first time by the electrophilic fluorination of azulenes with N-fluoro reagents. Selective preparation of 1-fluoroazulenes were performed by the fluorination of methyl azulene-1-carboxylates, followed by demethoxycarbonylation in 100% H3PO4. 2-Substituted azulenes were fluorinated in higher yields. In the 1H NMR of 1-fluoroazulene, long-range JFH values were