نتایج جستجو برای: achiral
تعداد نتایج: 1375 فیلتر نتایج به سال:
We report the first catalytic asymmetric cyanation of N-Boc ketoimines, which enables highly enantioselective synthesis of oxindole based α-amino nitriles. An unprecedented tandem aza-Wittig/Strecker reaction is also developed, emerging as a promising strategy for the catalytic asymmetric cyanation of ketoimines formed in situ from achiral ketones.
Helical nano-ribbons with a large aspect ratio were obtained through the self-assembly of an achiral amphiphile. The symmetry breaking is attributed to the orderly but twisted stacking of terpyridine groups. In addition, the morphology of the assemblies can be tuned by the coordination between terpyridine and Zn(2+) ion.
A little gold goes a long way: as little as 0.01 mol % of chiral gold phosphate is sufficient to afford the asymmetric transfer hydrogenation of quinolines with high stereoselectivity (up to 98 % ee). The achiral ligands on gold were found to have considerable effect on the catalytic efficiency.
A highly stereoselective one-pot procedure involving an enantioselective Michael addition promoted by low loading of an amino-squaramide catalyst followed by an achiral base catalyzed domino Michael-Knoevenagel-type 1,2-addition sequence provides efficient access to fully substituted cyclohexanes bearing five contiguous stereogenic centers in good yields (68-86%) and excellent stereoselectiviti...
A highly diastereoselective Ugi reaction involving a chiral cyclic imine, two enantiomerically pure isocyanides and various carboxylic acids was employed for the synthesis of polyfunctionalized pyrrolidines. Both chiral substrates have been efficiently prepared by chemoenzymatic methodologies from readily available achiral substrates. This highly convergent approach can find an application in t...
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