Catalytic Asymmetric Aldol Reaction of Trimethoxysilyl Enol Ethers Using 2,2′-Bis(di-p-tolylphosphino)-1,1′-binaphthyl·AgF Complex

Abstract

Catalytic asymmetric Mukaiyama-type aldol reaction using trimethoxysilyl enol ethers was achieved using 2,2′-bis(di-p-tolylphosphino)-1,1′-binaphthyl (p-Tol-BINAP)·AgF complex as a catalyst. The chiral silver(I) catalyst was easily generated by mixing p-Tol-BINAP and silver(I) fluoride in MeOH at room temperature. High syn- and enantioselectivities were obtained from both the E- and Z-silyl enol ethers. Use of a 1 : 1 mixture of MeOH and acetone as a solvent in the reaction of cyclohexanone-derived trimethoxysilyl enol ethers resulted in higher enantioselectivity.

Lewis Base Catalysis in Organic Synthesis

“…[222, 227a-b, 314] An alternative strategy for developing an asymmetric, fluoride-catalyzed reaction of silylated pronucleophiles would be to combine the achiral, n-s* catalysis provided by fluoride ions with traditional chiral Lewis acid catalysis. This strategy has been reduced to practice in aldol reactions, [380] allylations, [381] cyanomethylations, [382] vinylations, and phenylations [383] with silylated pronucleophiles. The most thoroughly investigated examples in this class of reactions are silver(I) fluoride and copper(I) fluoride catalyzed aldol reactions.…”

Aqueous Asymmetric Mukaiyama Aldol Reaction Catalyzed by Chiral Gallium Lewis Acid with Trost‐Type Semi‐Crown Ligands

“…Aldol products, 4a, [3] 4b, [8] 4c, [5] 4d, [4] 4e, [3] 4f, [5] 4g, [8] 4h, [4] 7a, [7] 7b, [9] 7c, [10] 7d, [11] 7e, [12] 10a, [6] 10b, [5] 13a, [4] 13c, [5] 13e [5] are known compounds.…”

Asymmetric Allylation of Carbonyl Compounds Catalyzed by a Chiral Phosphine–Silver Complex

“…However, the use of a 2:1 mixture of these catalysts reduced both the yield and the enantioselectivity to a great extent (Table , entry 5). In our aforementioned previous study on the chiral silver(I)‐catalyzed asymmetric Sakurai–Hosomi‐type allylation of aldehydes, we showed that a considerable amount of an inert 2:1 complex of BINAP/silver(I) salt was formed accompanied by a reactive 1:1 complex if BINAP was added to an equimolar amount of the silver(I) salt in CH 3 OH. In the reaction, a 0.6:1 mixture of BINAP/silver(I) salt was found to give the desired 1:1 complex without the formation of the 2:1 complex.…”