185152-35-6Relevant articles and documents
Knoevenagel-Doebner condensation promoted by chitosan as a reusable solid base catalyst
Anbu, Nagaraj,Hariharan, Surendran,Dhakshinamoorthy, Amarajothi
, (2020)
The development of green and sustainable processes using naturally occurring biopolymers is becoming one of the suitable remedies to replace the conventional catalytic systems that generate large amount of byproducts with high risk factors. In this context, although Knoevenagel-Doebner condensation reaction has been reported with many organocatalysts including proline, no attempts were made to develop heterogeneous catalysts with environmental concerns. Considering these factors in mind, the title reaction is studied with chitosan as a heterogeneous solid base catalyst for the synthesis of α,β-unsaturated carboxylic acids through the condensation followed by decarboxylation reactions. Chitosan offers many advantages including high stability as evidenced by leaching, reusability tests, wide substrate scope and providing higher yields of the desired products with high purity. Powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR), scanning electron microscope (SEM) and elemental analysis revealed that there are no major changes in the structural integrity and morphology of chitosan before and after catalysis under the optimized reaction conditions.
Polymer-assisted solution-phase synthesis under combined ultrasound and microwave irradiation: Preparation of α,β-unsaturated esters and carboxylic acids, key intermediates of novel sigma ligands
Rossi,Urbano,Baraglia, A. Carnevale,Serra,Bergamelli,Iannelli,Azzolina,Collina
experimental part, p. 3254 - 3262 (2011/03/18)
The optimal conditions to prepare α,β-unsaturated methyl esters via Wittig reaction combining polymer-assisted solution-phase synthesis (PASPS) methodology and simultaneous ultrasound and microwave irradiation were established. The effects of temperature, solvent, and irradiation time were discussed. Results clearly indicated the superiority of combined ultrasound and microwave-assisted procedure over microwave-assisted methodology. Moreover, an efficient PASPS procedure to prepare α,β-unsaturated carboxylic acids via tandem Wittig olefination and hydrolysis reaction was developed under combined ultrasound and microwave irradiation. Generally, a good conversion of aldehydes to acids was observed. The optimized protocols allowed us to quickly prepare a small collection of either α,β-unsaturated esters or carboxylic acids, key intermediates for the drug-discovery process of new sigma ligands. Copyright Taylor & Francis Group, LLC.
