A Convenient Method for the Preparation of Secondary Propargylic Ethers. The Reactions of Acetals with 1-Trimethylsilyl-1-alkynes Promoted by the Combined Use of Catalytic Amounts of Tin(IV) Chloride and Zinc Chloride
SnCl4 and ZnCl2, acetals undergo a coupling with 1-trimethylsilylalkynes to give secondary propargylic ethers in good yields. Similarly, propargylic ethers are directly produced from aldehydes by the treatment with alkoxytrimethylsilanes and 1-trimethylsilylalkynes under the same conditions. This catalyst system also efficiently promotes aldol reaction of silylenolethers with acetals or aldehydes, and
Bismuth Trichloride as a New Efficient Catalyst in the Aldol Reaction and the Michael Reaction
作者:Makoto Wada、Eiji Takeichi、Takashi Matsumoto
DOI:10.1246/bcsj.64.990
日期:1991.3
In the presence of a catalytic amount of bismuth(III) trichloride (5 mol%), silyl enol ethers react with aldehydes at room temperature in dichloromethane to give the corresponding aldols in good yields. Silyl enol ethers also have been found to react with α,β-unsaturated ketones at room temperature in dichloromethane to afford the corresponding 1,5-dicarbonyl compounds, the Michael adducts in good
Magnesium Chloride-Promoted Michael Addition of Dimethylsilyl Enolates to α-Enones
作者:Katsukiyo Miura、Akira Hosomi、Takahiro Nakagawa
DOI:10.1055/s-2003-41467
日期:——
In the presence of MgCl 2 , dimethylsilyl (DMS) enolates 1 smoothly reacted with α-enones in DMF to form1,5-diketones 3 in moderate to high yields. The Michael addition proceeded with moderate to high anti-diastereoselectivity.
New effective catalysts for Mukaiyama-aldol and -Michael reactions: bismuth trichloride-metallic iodide systems
作者:Christophe Le Roux、Hafida Gaspard-Iloughmane、Jacques Dubac、Joel Jaud、Pierre Vignaux
DOI:10.1021/jo00059a040
日期:1993.3
Metallic iodide-activated bismuth(III) chloride efficiently catalyzes the Mukaiyama-Aldol and -Michael reactions. Some examples of reactions of silyl enol ethers derived from acetophenone and cyclohexanone (I and 2, respectively) with aldehydes, ketones, acetals, and alpha-enones are given. The cross-over aldolization between 1 and benzaldehyde in the presence of BiCl3-l.5ZnI2 or BiCl3-1.5SnI2 systems (5 % mol) has been carried out quantitatively at -30 and -78-degrees-C, respectively. For this reaction a similar activation has been also observed with antimony(III) chloride. X-ray patterns of catalytic systems show the formation of bismuth(III) iodide by CI/I-exchange reaction between BiCl3 and metallic iodide (NaI, ZnI2, SnI2,...). These results.have been rationalized with a two-step mechanism in which a key feature seems to be the activating role played by BiI3 toward the cleavage of the Bi-chelate intermediate by the chlorosilane formed. Ultrasound activates significantly the catalytic power of these metallic halide systems.
Highly Selective 1,2- and 1,4-Addition of Silyl Enol Ethers to α,β-Unsaturated Carbonyl Compounds in 5 M Lithium Perchlorate−Nitromethane Medium