Repeated Use of the Catalyst in Ln(OTf)<sub>3</sub>-Catalyzed Aldol and Allylation Reactions
作者:Shu Kobayashi、Iwao Hachiya、Yoshinori Yamanoi
DOI:10.1246/bcsj.67.2342
日期:1994.8
triflate)-catalyzed aldol reactions of silyl enol ethers with aldehydes and allylation reactions of tetraallyltin with aldehydes proceeded smoothly in a water–ethanol–toluene system. The reactions proceeded much faster in the above solvent than in water–tetrahydrofuran. Repeated use of the catalyst in these reactions was realized by a very simple procedure.
Aldolreactionsbetweenaldehydes and trimethylsilylenolate; generated from ketones or thioesters proceeded smoothly in the presence of a Lewis base catalyst such as tetrabutylammonium phenoxide or p-methoxyphenoxide in THF to afford the corresponding aldols in high yields with high syn-selectivity.
Scandium trisdodecylsulfate (STDS). A new type of lewis acid that forms stable dispersion systems with organic substrates in water and accelerates aldol reactions much faster in water than in organic solvents
作者:Shū Kobayashi、Takeshi Wakabayashi
DOI:10.1016/s0040-4039(98)01081-8
日期:1998.7
A newtype of Lewisacid, scandium trisdodecylsulfate (STDS), was prepared. In the presence of a catalytic amount of STDS, aldol reactions of silyl enol ethers with aldehydes proceeded smoothly in water without using any organic solvents. It was proven that stable dispersion systems including the catalyst and organic substrates were formed in water and that catalytic activity in water was much higher
An iron(II) complex with a hindered hydroxyethyl-pybox (hepybox) ligand shows improved catalytic activity and enantioselectivity for asymmetric Mukaiyama-aldol reactions in aqueous media. This water-stable chiral Lewis acid promotes condensation of aromatic silyl enol ethers with a range of aldehydes with good yields, excellent syn-diastereoselectivity and up to 92% ee. The combination of the same ligand with Zn-II salt is also demonstrated as a remarkably efficient and water-compatible chiral Lewis acid.