Enantioselective aza-Henry reaction of t-Boc protected imines and nitroalkanes with bifunctional squaramide organocatalysts

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).


Enantioselective Michael Addition of Nitroalkanes to Nitroalkenes Catalyzed by Chiral Bifunctional Quinine-Based Squaramides
KANBEROĞLU, Esra; Tanyeli, Cihangir (2016-01-01)
A family of chiral bifunctional acid-/base-type quinine/squaramide organocatalysts is shown to be highly active promoters of the conjugate addition of 1-nitropropane to various trans--nitroalkenes. The cooperation of the quinine and the sterically encumbered squaramide moieties catalyzed the Michael addition reactions at 0 degrees C by using a catalyst loading of only 2mol% to afford the 1,3-dinitro Michael adducts with excellent enantioselectivity and diastereoselectivity (up to 95%ee and syn/anti isomers ...
Enantioselective sulfa-Michael addition reaction of methyl thioglycolate to chalcones derivatives with sterically encumbered quinine squaramide organocatalyst
HASILCIOĞULLARI, DENİZ; Tanyeli, Cihangir (2018-04-04)
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...
Enantioselective synthesis of furyl-substituted pyrrolidines
Araz, Mihrimah; Doğan, Özdemir; Department of Chemistry (2019)
Asymmetric 1,3-Dipolar Cycloaddition (DC) reactions of azomethine ylides are important for the synthesis of pyrrolidines. These reactions may give enantiomerically pure compounds in the presence of a chiral catalyst in a single step. Therefore, many groups have studied this reaction to synthesize aryl-substituted pyrrolidines in enantiomerically rich form. Although the aryl-substituted pyrrolidine synthesis is very common, the studies involving the heteroaryl-substituted pyrrolidines are quite rare. In gene...
Enantioselective Friedel-Crafts alkylation of indole with nitroalkenes in the presence of bifunctional squaramide organocatalysts
Dündar, Esra; Tanyeli, Cihangir (2021-01-01)
A series of chiral bifunctional quinine and 2-aminoDMAP based squaramide organocatalysts are evaluated in Friedel-Crafts alkylation of indoles with nitroolefins. These 3-substituted indole derivatives are synthesized in the presence of sterically encumbered tert-butyl squaramide/quinine with high enantioselectivity (up to >99% ee) and moderate chemical yields (up to 80%) by representing as chiral precursors for very important biologically active molecules. Besides, this asymmetric transformation provides a ...
Organocatalytic enantioselective construction of isatin-derived N-alkoxycarbonyl 1,3-aminonaphthols via sterically encumbered hydrocarbon-substituted quinine-based squaramide
Karahan, SEDA; Tanyeli, Cihangir (2017-09-07)
Herein, an illustrative example to synthesize chiral naphthoxazepine precursors via the aza-Friedel-Crafts reaction of N-alkoxycarbonyl isatin ketimines with naphthol using a new 2-adamantyl-substituted quinine-derived squaramide catalyst is presented; the reaction afforded the chiral-tetrasubstituted 3-amino-2-oxindoles with excellent enantioselectivity of greater than 99% ee and quantitative yields. To the best of our knowledge, this methodology is featured for being representative of the efficiency of st...
Citation Formats
Z. D. Susam and C. Tanyeli, “Enantioselective aza-Henry reaction of t-Boc protected imines and nitroalkanes with bifunctional squaramide organocatalysts,” NEW JOURNAL OF CHEMISTRY, pp. 3555–3561, 2017, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/33133.