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Asymmetric synthesis of 2,3-dihydrofurans with bifunctional quinine / squaramide organocatalysts

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2019
Bozdemir, Merve
Organocatalytic asymmetric reactions are efficient and environmentally friendly methods to synthesize products with higher enantioselectivities. Asymmetric domino Michael-SN2 reactions are one of the type of organocatalytic reaction frequently used to form carbon-carbon bonds in the synthesis of the derivatives of dihydrofurans, which are intermediates mainly utilized as precessor materials in the pharmaceutical fields. In this thesis, the reaction occuring between acetylacetone and (Z)-(2-bromo-2-nitrovinyl)benzene was chosen as a model reaction. As a first step, bifunctional 2-aminoDMAP and quinine-anchored squaramide organocatalysts were tested. Then, quinine / t-butyl squaramide organocatalyst was identified as the most suitable organocatalyst for our reaction. Subsequently, optimization studies were done and using different α-bromonitroalkenes and 1,3-dicarbonyl compounds, 14 different derivatives were synthesized. In optimized conditions with 10 mol% organocatalyst loading, the best result gave 97 % enantiomeric excess.