[GRAPHICS]A new intermolecular metathesis between a variety of alkynes and alkyl enol ethers is described. The best results were obtained with the second generation Grubbs' precatalysts. The reaction occurred with a high degree of regioselectivity and provided electron-rich dienes, which underwent a variety of [4 + 2] cycloadditions.
Metal Carbene-Promoted Sequential Transformations for the Enantioselective Synthesis of Highly Functionalized Cycloheptadienes
摘要:
A two-step, three-component coupling of an alkyne, enol ether, and vinyl diazoester was accomplished by use of successive metal carbene-catalyzed transformations. This efficient approach to cycloheptadienes is both diastereo- and enantioselective. Kinetic resolution was accomplished on dienol ethers bearing a racemic chiral center at the propargylic position. A model is offered which explains the observed selectivity and accounts for the reactivity difference between trans- and cis-dienol ethers.
An efficient synthesis of 3-substituted crotonaldehydes via alkyne-enol ether cross-metathesis in the presence of CuSO4 and in aqueous medium was developed. Crotonaldehydes were obtained in good yields from terminal aryl-alkynes as well as from terminal alkyl-alkynes. All of the reactions were carried out under microwave irradiation and were completed in a few minutes. Water was used as the cosolvent, making c, this approach safer, economic, and desiderable from an enviromental point of view.
Metal Carbene-Promoted Sequential Transformations for the Enantioselective Synthesis of Highly Functionalized Cycloheptadienes
作者:Liang Deng、Anthony J. Giessert、Oksana O. Gerlitz、Xing Dai、Steven T. Diver、Huw M. L. Davies
DOI:10.1021/ja045173t
日期:2005.2.1
A two-step, three-component coupling of an alkyne, enol ether, and vinyl diazoester was accomplished by use of successive metal carbene-catalyzed transformations. This efficient approach to cycloheptadienes is both diastereo- and enantioselective. Kinetic resolution was accomplished on dienol ethers bearing a racemic chiral center at the propargylic position. A model is offered which explains the observed selectivity and accounts for the reactivity difference between trans- and cis-dienol ethers.
Intermolecular Enol Ether−Alkyne Metathesis
作者:Anthony J. Giessert、Lee Snyder、Jordan Markham、Steven T. Diver
DOI:10.1021/ol034459k
日期:2003.5.1
[GRAPHICS]A new intermolecular metathesis between a variety of alkynes and alkyl enol ethers is described. The best results were obtained with the second generation Grubbs' precatalysts. The reaction occurred with a high degree of regioselectivity and provided electron-rich dienes, which underwent a variety of [4 + 2] cycloadditions.