Pseudo-five-component organocatalyzed synthesis of dicyanoanillines using only malononitrile and aromatic aldehydes

Abstract

General procedure for the synthesis of Knoevenagel products 4 [1] Malononitrile (2.0 mmol) and the aldehyde (2.0 mmol) were dissolved in 2 mL of EtOH in a 10 mL flask tube and one drop of Et 3 N was added to this mixture. After stirring at room temperature for 2 h, the solid was filtered to obtain the crude product. Further purification was done by flash chromatography on silica gel using EtOAc/hexanes (1:4) as the eluent.The procedure for the synthesis of malononitrile dimer 5 [2] To a cooled solution of 25 mmol of NaOH in 10 ml of the corresponding alcohol, 3.3 g (50 mmol) of malononitrile was added. The temperature was slowly increased and the mixture was stirred under reflux. After 30 min of heating the mixture was cooled and the solid was filtered off, washed with cold alcohol and dried. After dissolving the solid in water, it was acidified with conc. HCl to pH = 4, the product was filtered off and recrystallized from water to obtain the pure product 5.

Pseudo-multicomponent reactions

“…In 2022 M. Mojtahedi and co-workers 70 reported a novel pseudo-5CR synthesis of dicyanoanilines 409a–k by reacting different substituted aromatic aldehydes 396a–k with four equivalents of malononitrile ( 397 ) in the presence of triethylamine. To explain this transformation the authors proposed the following reaction mechanism: the first step is a Knoevenagel condensation of the aldehydes 396 with a molecule of malononitrile to produce the intermediates 398 .…”