A catalytic amount of KF.18-crown-6 complex is effective as a soluble fluoride source to activate an asymmetric Sakurai-Hosomi allylation with BINAP and silver(I) triflate catalyst. The allylation of a variety of aromatic, alpha,beta-unsaturated and aliphatic aldehydes with allylic trimethoxysilane resulted in high yields and remarkable enantioselectivities. In addition, the asymmetric Mukaiyama-type
New catalytic asymmetric Mukaiyama-type aldol reaction using trimethoxysilyl enol ethers was achieved using p-Tol-BINAP · AgF complex as a catalyst. High syn- and enantioselectivities were obtained both from the E- and Z-silyl enol ethers.
以对 Tol-BINAP - AgF 复合物为催化剂,利用三甲氧基硅基烯醇醚实现了新的催化不对称 Mukaiyama 型醛醇反应。E 型和 Z 型硅烷烯醇醚均获得了较高的合成和对映体选择性。
Catalytic Asymmetric Aldol Reaction of Trimethoxysilyl Enol Ethers Using 2,2′-Bis(di-<i>p</i>-tolylphosphino)-1,1′-binaphthyl·AgF Complex
Catalytic asymmetric Mukaiyama-type aldolreaction 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
The aldol reactions of trimethoxysilyl enol ethers catalyzed by lithium binaphtholate were found to be powerful tools for the construction of quaternary asymmetric carbon centers. The stereoselectivities were greatly affected by the presence of water. Trimethoxysilyl enol ether derived from a cyclic ketone, such as cyclohexanone, was used as a substrate to obtain the anti-adduct preferentially under anhydrous conditions; by contrast, the syn-adduct was preferentially obtained under aqueous conditions with high stereoselectivity. The aldol-Tishchenko reaction of a trimethoxysilyl enol ether derived from acyclic ketones proceeded to give monoacyl 1,3-diol derivatives in high enantioselectivities. (C) 2012 Elsevier Ltd. All rights reserved.
Enantioselective Aldol Reaction of Trimethoxysilyl Enol Ether Catalyzed by Lithium Binaphtholate
(GRAPHICS)An aldol reaction of trimethoxysilyl enol ether catalyzed by lithium binaphtholate, in which water serves as an additive and plays a pivotal role in stereoselectivitles, was developed. This is the first example of an aldol reaction of trimethoxysilyl enol ether catalyzed by a chiral base.