473845-04-4Relevant articles and documents
Catalytic asymmetric allylation of aldehydes and related reactions with bis(((S)-binaphthoxy)(isopropoxy)titanium) oxide as a μ-oxo-type chiral Lewis acid
Hanawa, Hideo,Uraguchi, Daisuke,Konishi, Shunsuke,Hashimoto, Takuya,Maruoka, Keiji
, p. 4405 - 4413 (2003)
A new, chiral bis-TiIV of type 3 has been designed and can be utilized for strong activation of aldehyde carbonyls, thereby allowing a new catalytic enantioselective allylation of aldehydes with allyltributyltin. The chiral bis-TiIV catalyst (S,S)-3 can be readily prepared either by treatment of bis(triisopropoxy)titanium oxide with (S)-BINOL or by treatment of ((S)-binaphthoxy)isopropoxytitanium chloride with silver(I) oxide. Treatment of hydrocinnamaldehyde with allyltributyltin under the influence of chiral bis-TiIV oxide (S,S)-3 generated in situ (10 mol%) in CH 2Cl2 afforded an allylation product in 84% yield and with 99% ee. This asymmetric allylation with non-racemic bis-TiIV oxide 3 and partially resolved (S)-BINOL shows a positive nonlinear effect in correlation of the enantiopurity of the allylation product with the ee of the (S)-BINOL. Chiral bis-TiIV oxide (S,S)-3 can also be utilized for related reactions such as asymmetric methallylation and propargylation of aldehydes with high enantioselectivity. This asymmetric approach provides a very useful way of obtaining high reactivity and selectivity through the simple introduction of the M-O-M unit into the design of chiral Lewis acid catalysts.
