Impact of a homogeneous hydrogen bond catalysis for the ethyl (hetero)arylidene cyanoacetate preparation in the presence of TMDP

The synthesis of ethyl (hetero)arylidene cyanoacetates, valuable intermediates in organic chemistry, has been investigated using several commercially available and synthetic nitrogen-based organocatalysts. 4,4′-Trimethylenedipiperidine (TMDP) was chosen as an efficient organocatalyst regarding short reaction times, excellent yield with a conversion of 100%, and high selectivity. The pure products could be isolated and devoid of a costly workup. The residue could be directly reused for the next catalytic run. Encouragingly, TMDP exhibited chemical stability and high recyclability in five subsequent runs without a significant loss in catalytic activity. Scale-up experiments also demonstrate the current strategy’s promising industrial application. Mechanistic studies were conducted to provide insights into the reaction pathways and possible interaction/reaction between organocatalyst and each reactant through performing control experiments and studying FTIR in neat state and NMR spectra in aprotic and protic deuterated solvents. The developed metal-free and halogen-free catalytic strategy offers cost-effectiveness, low toxicity, and enhanced sustainability.