Enantioselective synthesis of 2,3-dihydrofurans using a bifunctional quinine/squaramide organocatalyst

Asymmetric organocatalytic domino type Michael-S(N)2 reactions give access to enantiomerically enriched dihydrofuran derivatives that can be used as valuable chiral building blocks. A variety of alpha-bromonitroalkenes and 1,3-dicarbonyl compounds were allowed to react under optimized conditions, in the presence of a bifunctional quinine-derived sterically encumbered squaramide (H-bond donor) organocatalyst. The conditions developed in this article have great advantages over the methods known in the literature in terms of reaction duration (1-6 h vs. 24-96 h) and reaction temperature (room temperature vs. -20 degrees C to -50 degrees C) giving rise to quite diastereoselective products with good enantioselectivities up to 97% ee.


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Asymmetric organocatalytic sulfa-Michael reactions give access to enantiomerically enriched sulfur containing adducts that can be used as valuable chiral building blocks. A variety of chalcone derivatives were allowed to react with methyl thioglycolate under optimized conditions, in the presence of a bifunctional quinine derived sterically encumbered squaramide organocatalyst, giving rise to excellent stereoselectivities, up to 99% ee. The designed catalyst system proved to be efficient even at gram scale a...
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Pyrrolopyrazinone, triazinone and oxazinone derivatives were synthesized via practical methodologies. In the study, N-alkyne substituted pyrrole esters were synthesized and isolated as key compounds via copper catalyzed cross-coupling reaction. Then, key compounds underwent nucleophilic cyclization reaction with hydrazine monohydrate to yield pyrrolopyrazinone and/or pyrrolotriazinone derivatives according to electronic properties of group attached to alkyne unit. Additional study was the synthesis of pyrro...
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Enantioselective aza-Henry reaction of t-Boc protected imines and nitroalkanes with bifunctional squaramide organocatalysts
Susam, Zeynep Dilşad; Tanyeli, Cihangir (2017-05-07)
An organocatalytic asymmetric aza-Henry reaction of t-Boc protected imines with nitroalkanes has been established by chiral acid-base type bifunctional Cinchona alkaloid/squaramide organocatalysts. The cooperation of a quinine motif as a base and sterically encumbered squaramide (H-bond donor) enabled mostly complete conversion of a range of reactants into the corresponding aza-Henry products at room temperature with good selectivities (up to 91% ee with 10 mol% catalyst loading).
Citation Formats
Z. D. Susam, G. Gundogdu, and C. Tanyeli, “Enantioselective synthesis of 2,3-dihydrofurans using a bifunctional quinine/squaramide organocatalyst,” NEW JOURNAL OF CHEMISTRY, pp. 0–0, 2021, Accessed: 00, 2021. [Online]. Available: https://hdl.handle.net/11511/94993.