Asymmetric synthesis, also called chiral synthesis, enantioselective synthesis or stereoselective synthesis, is organic synthesis which introduces one or more new and desired elements of chirality. This is important in the field of pharmaceuticals and organic chemistry because the different enantiomers or diastereomers of a molecule often have different biological activity. Use of catalysts is one of the most effective methods preferred by the researchers in recent years. It causes to the preferential formation of a stereoisomer rather than a constitutional isomer. In this study, tetraoxocalixarenetriazine was synthesized firstly by using resorcinol and cyanuric chloride and then this starting material was derivatized with (R)-(-)-2-phenylglycinol to obtain tetraoxocalixarenetriazine based chiral compound. Characterization of tetraoxocalixarenetriazine was done by 1H and 13C NMR spectroscopy which is depicted in literature. Then, new organocatalyst, which possess a hydroxyl and an amino group, was designed and synthesized. The structure of the receptor characterized by FTIR, 1H and 13C NMR spectroscopy, elemental analysis and optical rotation measurement was also included. The newly prepared tetraoxacalixarenetriazine derivative was employed as a chiral ligand in the enantioselective Michael addition of dimethylmalonate to conjugated nitroalkenes and good to excellent enantioselectivities were obtained. Various factors, (solvent, temperature, catalyst %) were examined and the reactions were optimized. The best condition for the Michael addition reaction was determined as room temperature, toluene as solvent and 10 mol% of heteroatom-bridged calixaromatic based chiral catalyst as organocatalyst loading. The catalytic efficiency of the chiral catalyst was analyzed by HPLC using chiral columns. The corresponding adducts were generally obtained in (S)-forms with high yields (up to 93%) and with high to excellent enantioselectivities (up to 95% ee).
Yayımlanma Tarihi : 31 Aralık 2019
|APA||Genç, H . (2019). An Efficient Synthesis of Chiral Catalyst: Application in Enantioselective Michael Addition Reactions . Avrupa Bilim ve Teknoloji Dergisi , (17) , 20-28 . DOI: 10.31590/ejosat.598343|