Dramatic titanium alkoxide effect in the catalytic enantioselective addition of dialkylzincs to aldehydes
作者:Stefan Nowotny、Stephan Vettel、Paul Knochel
DOI:10.1016/s0040-4039(00)60721-9
日期:1994.6
The use of Ti(Ot-Bu)4, or related bulky titanium(IV) alkoxides, as cocatalysts instead of Ti(Oi-Pr)4 in the enantioselective addition of dimethylzinc to aldehydes in the presence of the catalyst 2 (8 mol%) leads to a dramatic improvement of the enantioselectivity (0%ee to 93%ee). The scope and the limitations of this effect are described.
Kinetic resolution of γ-iodo allylic alcohols by the Sharpless asymmetric epoxidation reaction proceeds with very large rate differences for the two enantiomers, thus providing a highly efficient method for preparation of optically pure . The alcohols thus prepared can be readily converted into various secondary allylic alcohols through the coupling reaction with nucleophiles.
A practical, efficient method for preparation of four possible stereoisomers of secondary allylic alcohols using kinetic resolution of (E)-1-trimethylsilylalk-1-en-3-ol by the sharpless process
作者:Yasunori Kitano、Takashi Matsumoto、Fumie Sato
DOI:10.1039/c39860001323
日期:——
Kineticresolution of (E)-1-trimethylsilylalk-1-en-3-ol by the Sharplessprocess, which proceeds with very large rate differences for the two isomers, combined with the reactivity of epoxysilyl compounds affords a practical, efficientmethod for preparation of fourpossiblestereoisomers of secondaryallylicalcohols.