Yb(OTf)(3) with TMSCl or TMSOTf catalyzed an imino enereaction. The reaction of N-tosylbenzaldimine (1) with alpha-methylstyrene (2) proceeded smoothly to give homoallylic amine 3 in the presence of a catalytic amount of Yb(OTf)(3) and TMSCl. This catalytic system was successfully applied to the imino enereactions of various aldimines with alkenes. This new imino enereaction provides a unique method for
Yb(OTf)(3), can catalyze the glyoxylate-ene reaction effectively as a water-stable and reusable catalyst. Moreover, the selectivity of DA product or ene product can be adjusted by solvents in the reaction of glyoxylates with a diene (isoprene). In the presence of chiral ytterbium complexes generated in situ from Yb(OTf)(3) and optical 6,6'-disubstituted binaphthols, methyl glyoxylate smoothly reacts with alpha-methyl styrene to afford alpha-hydroxyl esters in modest optical yields. (C) 1997 Elsevier Science Ltd.
Synthesis of Novel Chiral Spiro Bis(pyrazole) Ligands
作者:Hiroaki Sasai、Shinobu Takizawa、Yuji Honda、Midori A. Arai、Takahiro Kato