Efficient Activation of Acetals, Aldehydes, and Imines toward Silylated Nucleophiles by the Combined Use of Catalytic Amounts of [Rh(COD)Cl]<sub>2</sub>and TMS-CN under Almost Neutral Conditions
In the presence of a catalytic amount of a transition metal compound such as [Rh(COD)Cl]2, Co(acac)2, or NiCl2, trimethylsilyl cyanide smoothly reacts with acetals to form α-methoxy carbonitriles in good yields. In the coexistence of catalytic amounts of [Rh(COD)Cl]2 and TMS-CN, silyl enol ethers or ketene silyl acetals react with acetals, aldehyes, or imines to yield the corresponding coupling products in good yields under almost neutral conditions.
Lanthanide Trifluoromethanesulfonates as Reusable Catalysts: Aldol Reactions in Organic Solvents
作者:Shū Kobayashi、Iwao Hachiya、Takeshi Takahori
DOI:10.1055/s-1993-25864
日期:——
The aldol reaction of silyl enolates with aldehydes or acetals using a lanthanide trifluoromethanesulfonate as catalyst smoothly proceed in organic solvents to afford the corresponding aldol-type adducts in high yields. The catalyst can be easily recovered after the reaction is completed, and yields of the 2nd run of the catalyst are comparable to those of the 1st run.
A catalytic amount of tris(p-bromophenyl)aminium hexachloroantimonate promoted the substitution reactions of dimethylacetals with various silylatednucleophiles through an electron transfer mechanism. Silyl compounds include silyl enol ether, ketene silyl acetal, and allylsilane. One methoxy group of the substrates was effectively substituted by nucleophiles to form carbon-carbon bonds.
Chemoselective Aldol Reaction of Silyl Enolates Catalyzed by MgI<sub>2</sub> Etherate
作者:Wei-Dong Z. Li、Xing-Xian Zhang
DOI:10.1021/ol026585e
日期:2002.10.1
Mukaiyama-type aldol coupling of typical silyl enolates 2-4 with aryl or vinyl aldehydes and acetals was realized in the presence of 1-5 mol % of MgI(2) etherate (1) in a mild, efficient, and highly chemoselective manner. Iodide counterion, weakly coordinating peripheral ethereal ligands (Et(2)O) of Mg(II), and a noncoordinating reactionmedia (i.e. CH(2)Cl(2)) are among the critical factors for the
Catalytic amounts of triarylpyrylium saltsphotochemically and thermally promoted the substitution reactions of dimethyl acetals with silylated nucleophiles.