A tandem S N 2 alkylation/Michael addition to vinylogous carbonates based approach for the stereoselective synthesis of benzoxepines is developed.
A remarkable organocatalyst that facilitates the asymmetric Michael addition of cyclic ketones to nitroolefins in excellent stereoselectivities (98:2 to >99:1 dr, 92% to >99% ee) has been developed and afforded various types of optically active nitroalkane derivatives of synthetic and biological importance. The method is extended to the synthesis of benzopyranoxepines and benzoxepinopyridines with angular substituents. + 86‐22/23582458 . Author links open overlay panel Uwe Eilitz Frank Leßmann Oliver Seidelmann Volkmar Wendisch. E-mail address: … Wen Juan Ruan. E-mail address: wjruan@nankai.edu.cn. The steroselective oxa‐Michael addition of the phenol moiety present in tyrosine and 3‐iodotyrosine to different propargyl aldehydes delivered products with predominantly Z stereochemistry, as evidenced by X‐ray crystallography analysis. Asymmetric aza-Michael addition 1 to nitro alkenes is a powerful method to synthesize valuable chiral molecules which are useful building blocks for organic synthesis. The aza-Michael addition reaction was conducted under the same conditions as described by Philp et al. Stereoselective Michael addition, one of the most important organocatalytic reactions usually serves as a key stereoinduction transformation. Journal Home. DOI: 10.1021/ol900330p. Department of Chemistry, Nankai University, Tianjin, 300071, P. R. China, Fax: (internat.) The Michael addition of benzylamine to the homochiral methylenebutanedioate 10 gave an adduct 11 in good yield with high stereoselectivity.
Organocatalysts feature pyrrolidine unit for enamine activation of aldehydes and hydrogen bond donating fragment for nitroalkene activation.
Stereoselective addition of nitromethane to conjugated en‐ynones was performed through the application of chiral squaramides. Journal Name: Letters in Organic Chemistry. A stereoselective method for the synthesis of substituted tetrahydropyran derivatives employing a tandem SN2−Michael addition sequence to vinylogous carbonates is developed. Dedicated to Professor Klaus Burger on the occasion of his 65th birthday. The stereoselectivity improves with an increase in the steric bulk of the substituents. If the two-step mechanism described above is correct, and if the carbocation intermediate is sufficiently long-lived to freely-rotate about the sigma-bond component of the original double bond, we would expect to find random or non-stereoselective addition in the products. Author(s): Yang-Guo Li, Yang Zhang, Guang-Fen Du*, Cheng-Zhi Gu, Lin He*. Highly efficient stereoselective 1,4-addition of racemic α-fluoro-α-nitro(phenylsulfonyl)methane (FNSM) as a fluoromethyl pronucleophile to α,β-unsaturated ketones using a wide range of chiral organobifunctional catalysts under moderate conditions in the absence of an additional base has been achieved. Bifunctional squaramide and thiosquaramide organocatalysts were assessed in a stereoselective Michael addition of aldehydes to nitroalkenes. A series of catalysts was screened for the enantioselective addition …
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