'Chitosan in water' as an eco-friendly and efficient catalytic system for Knoevenagel condensation reaction
Dhiraj Rani1, Priyanka Singla1, Jyoti Agarwal1
1Department of Chemistry and Center of Advanced Studies, Panjab University, Chandigarh 160014, India.
Abstract:
The catalytic activity of commercially available chitosan has been investigated for the Knoevenagel reaction of ethylacetoacetate (EAA)/dimethylmalonate (DMM) with arylaldehydes. Among all the screened solvents, Chitosan performed the best in water as reaction medium. Substrate scope was evaluated by using various arylaldehydes and it was observed that presence of electron donating groups on aldehydes reduce the yields, while electron-withdrawing groups increase the yields. In case of the reaction of 4-bromobenzaldeyde with EAA, the lower yield of the corresponding product 14 was obtained due to the high stability of imine intermediate formed and this postulate was proved by experiments as well as theoretical calculations. In case of EAA, the E/Z stereochemistry of the corresponding products was assigned based on NOESY experiment.
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