7175-71-5Relevant academic research and scientific papers
Expansion of Azulenes as Nonbenzenoid Aromatic Compounds for C-H Activation: Rhodium- And Iridium-Catalyzed Oxidative Cyclization of Azulene Carboxylic Acids with Alkynes for the Synthesis of Azulenolactones and Benzoazulenes
Maeng, Chanyoung,Son, Jeong-Yu,Lee, Seung Cheol,Baek, Yonghyeon,Um, Kyusik,Han, Sang Hoon,Ko, Gi Hoon,Han, Gi Uk,Lee, Kyungsup,Lee, Kooyeon,Lee, Phil Ho
, p. 3824 - 3837 (2020/02/28)
Rhodium-catalyzed oxidative [4 + 2] cyclization reactions through the C-H activation of azulene carboxylic acids as nonbenzenoid aromatic compounds with symmetrical and unsymmetrical alkynes were developed under aerobic conditions, which produced azulenolactone derivatives with a wide substrate scope and excellent functional group tolerance. Interestingly, azulenic acids in reaction with alkynes underwent iridium-catalyzed [2 + 2 + 2] cyclization accompanied by decarboxylation to afford tetra(aryl)-substituted benzoazulene derivatives. The reactivity order for C-H activation reaction is greater toward azulene-6-carboxylic acid, azulene-1-carboxylic acid, and azulene-2-carboxylic acid. For the first time, the expansion of azulenes having directing group as nonbenzenoid aromatic compounds for C-H activation was successful, indicating that nonbenzenoid aromatic compounds can be used as good substrates for the C-H activation reaction. Therefore, the research area of C-H activation will certainly expand to nonbenzenoid aromatic compounds in future.
An easy access to 2-substituted azulenes from azulene-2-boronic acid pinacol ester
Fujinaga, Masayuki,Suetake, Kouichi,Gyoji, Kazuhiro,Murafuji, Toshihiro,Kurotobi, Kei,Sugihara, Yoshikazu
experimental part, p. 3745 - 3748 (2009/06/18)
Azulene-2-boronic acid pinacol ester was conveniently transformed into 2-substituted azulenes bearing carboxyl, formyl, ester, or amino groups, which are difficult to access by conventional methods. Furthermore, the azulene-2-carboxylic acid thus synthesized was subjected to the Ugi four-component condensation to obtain a dipeptide-type product containing an azulene skeleton. Georg Thieme Verlag Stuttgart.
