An unprecedented nucleophilic addition of piperidine on an electron acceptor, namely, 2‐(3‐oxo‐2,3‐dihydro‐1H‐cyclopenta[b]naphthalen‐1‐ylidene)malononitrile is reported. This unexpected behavior was observed during the synthesis of push‐pull dyes using the classical Knoevenagel reaction. To overcome this drawback, use of diisopropylethylamine (DIPEA) enabled to produce the expected dyes PP1 and PP2. The optical and electrochemical properties of the different dyes were examined. Theoretical calculations were also carried out to support the experimental results. To evidence the higher electron‐withdrawing ability of this electron acceptor, a comparison was established with two dyes (PP3 and PP4) comprising its shorter analogue.

中文翻译：

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哌诺酮通过Knoevenagel反应合成过程中对电子受体的前所未有的亲核攻击

据报道，哌啶在电子受体上空前的亲核加成，即2-（3-氧代-2,3-二氢-1H-环戊[ b ]萘-1-亚甲基）丙二腈。在使用经典的Knoevenagel反应合成推挽染料的过程中观察到了这种出乎意料的行为。为了克服该缺点，使用二异丙基乙胺（DIPEA）能够产生预期的染料PP1和PP2。检查了不同染料的光学和电化学性质。还进行了理论计算以支持实验结果。为了证明该电子受体具有更高的吸电子能力，我们对两种染料（PP3和PP4）包含其较短的类似物。