The squaramide-catalyzed asymmetric Michael/cyclization tandem reaction for the synthesis of chiral trifluoromethylated hydroxyimino tetrahydrobenzofuranones
An enantioselective synthesis of trifluoromethylated hydroxyimino tetrahydrobenzofuranones has been developed. 1,3-Dicarbonyl carbocyclic compounds react with β-CF3-β-disubstituted nitroalkenes in the presence of a chiral squaramide catalyst, providing efficient access to diverse hydroxyimino tetrahydrobenzofuranones featuring a trifluoromethyl group at the C3-position of an all-carbon quaternary stereocenter
Catalytic asymmetric synthesis of enantioenriched β-nitronitrile bearing a C-CF<sub>3</sub>stereogenic center
作者:Ajay Jakhar、Prathibha Kumari、Mohd Nazish、Noor-ul H. Khan、Rukhsana I. Kureshy、Sayed H. R. Abdi、E. Suresh
DOI:10.1039/c6ra00093b
日期:——
all-carbon quaternary stereogenic center have been synthesized via asymmetric cyanation reaction. In situ generated chiral TiIV salen complexes were used as catalysts for asymmetric addition of TMSCN to nitroolefins containing a trifluoromethylated prochiral center in the β-position, to afford the corresponding β-nitronitriles in excellent yield (up to 93%) with good enantioselectivity (up to 99%)
通过不对称氰化反应合成了具有全碳季立体中心的CF 3取代的β-腈。原位生成的手性Ti IV salen络合物用作催化剂,用于将TMSCN不对称加成到在β位上含有三氟甲基化手性中心的硝基烯烃中,从而以良好的对映选择性(良好的产率(高达93%))提供相应的β-腈(高达99%)。这种新开发的催化方案导致有效合成但有用的手性α,α'-二取代的β-氨基酸。
Enantioselective Michael Addition of Pyrazolin-5-ones to β-CF3-β-Disubstituted Nitroalkenes Catalyzed by Squaramide Organocatalyst
A highly enantioselectiveMichaeladdition of pyrazolin-5-ones with β-CF3-β-disubstituted nitroalkenes catalyzed by bifunctional squaramide has been developed. Various chiral β-CF3-β-5-hydroxy-pyrazolin-3-yl-disubstituted nitroalkane derivatives bearing all-carbon quaternary stereocenter were prepared in good yields (up to 88%) and excellent enantioselectivities (up to 97% ee).
The first examples of highly effective Henry reactions between nitroalkanes and aldehydes or trifluoromethyl ketones that proceed under catalyst-free and additive-free conditions, in a recyclable tap water medium, and at room temperature are reported. This process tolerates a broad range of aldehydes and trifluoromethyl ketones to give a series of β-nitro alcohol products in excellent yields. Such