The author of 《Enamine Catalytic Annulation of Azonaphthalenes: An Access to Indole Derivatives》 were Zhao, Hanhui; Yuan, Huijun; Zhang, Yanru; Li, Rongshi; Li, Wenjun. And the article was published in Organic Letters in 2019. Electric Literature of C9H7NO The author mentioned the following in the article:
The secondary-amine mediated [3 + 2] annulation of azonaphthalenes with aldehydes and ketones is described for the first time, which provides an alternative protocol for the synthesis of indole derivatives It features a cheap and readily available catalyst, a broad scope of reactants, very mild reaction conditions, and high efficiency. Significantly different from the transition-metal-mediated processes, the enamine activation represents the first organic base-catalytic protocol for indole synthesis.3-Oxo-3-phenylpropanenitrile(cas: 614-16-4Electric Literature of C9H7NO) was used in this study.
3-Oxo-3-phenylpropanenitrile(cas: 614-16-4) has been used in the synthesis of substituted naphtho[1,8-bc]pyrans. It was also used as building block in the preparation of 4H-pyrans, 2-pyridones, furans and carbocyclics.Electric Literature of C9H7NO
Referemce:
Nitrile – Wikipedia,
Nitriles – Chemistry LibreTexts