291776-02-8Relevant articles and documents
Squaramide-Linked Chloramphenicol Base Hybrid Catalysts for the Asymmetric Michael Addition of 2,3-Dihydrobenzofuran-2-carboxylates to Nitroolefins
Yan, Linjie,Huang, Guanxin,Wang, Haifeng,Xiong, Fangjun,Peng, Haihui,Chen, Fener
supporting information, p. 99 - 103 (2018/01/17)
An array of hybrid catalysts incorporating a chloramphenicol base moiety linked to another chiral scaffold through a squaramide linker were developed and successfully used in the Michael addition of 2,3-dihydrobenzofuran-2-carboxylates to nitroolefins. Control experiments suggested that the hybrid catalysts were more reactive than nonhybridized bifunctional catalysts, and matching of the chirality between the two scaffolds was crucial for high reactivity and stereoselectivity. These hybrid organocatalysts could be used with a variety of substrates. At a 0.5 mol-% catalyst loading, a range of 2,3-dihydrobenzofuran-2-carboxylates derivatives bearing quaternary and tertiary stereogenic centers were obtained in high yields (up to 98 %) with excellent enantioselectivities (up to 99 % ee) and moderate diastereoselectivities (up to 8:92 dr).
Trans -1,2-Diaminocyclohexane-based sulfonamides as effective hydrogen-bonding organocatalysts for asymmetric Michael-hemiacetalization reaction
Dajek, Maciej,Kowalczyk, Rafa?,Boratyński, Przemys?aw J.
, p. 4358 - 4363 (2018/09/11)
An easily attainable bifunctional monosulfonamide derivative of DACH was an effective catalyst for Michael addition-hemiacetalization reactions, providing products with ees exceeding 99% under optimized conditions. High enantioselectivities were achieved with just 0.2% mol catalyst loading. The sulfonamide outperformed analogous thiourea and squaramide-based organocatalysts.
Chemoenzymatic syntheses of novel ligands derived from trans-cyclohexane-1, 2-diamine: Application in the enantioselective addition of diethylzinc to aromatic aldehydes
Gonzalez-Sabin, Javier,Gotor, Vicente,Rebolledo, Francisca
, p. 449 - 454 (2007/10/03)
Enantiopure (1R,2R)-cyclohexane-1,2-diamine derivatives, easily prepared from the corresponding (±)-trans-2-dialkylaminocyclohexanols through a chemoenzymatic route, have been employed as ligands in the enantioselective addition of diethylzinc to aromatic aldehydes. Of all the ligands tested, C 2-symmetric bisaminoamides derived from pyridine-2,6-dicarboxylic acid proved to be the most efficient.
Chemoenzymatic preparation of optically active trans-cyclohexane-1,2- diamine derivatives: An efficient synthesis of the analgesic U-(-)-50,488
Gonzalez-Sabin, Javier,Gotor, Vicente,Rebolledo, Francisca
, p. 5788 - 5794 (2007/10/03)
Stereoespecific syntheses of (±)-trans-N,N-cyclohexane-1,2-diamines ((±)-4a-g) were carried out from the corresponding (±)-trans-N,N- dialkylaminocyclohexanols by successive treatment with mesyl chloride and aqueous ammonia. The stereochemical outcome indicates the formation of a meso-aziridinium ion intermediate, Kinetic resolutions of diamines (±)-4 were efficiently accomplished in aminolysis reactions catalyzed by lipase B from Candida antarctica with ethyl acetate as the solvent and acyl donor. Acetamides and the remaining diamines, isolated as the benzyloxycarbonyl derivatives, were obtained with very high ee values (92-99%), One of the carbamates was used as a precursor of the analgesic U-(-)-50,488.
