Stereoselective Suzuki−Miyaura Cross-Coupling Reactions of Potassium Alkenyltrifluoroborates with Alkenyl Bromides
作者:Gary A. Molander、Luciana A. Felix
DOI:10.1021/jo050286w
日期:2005.5.1
The stereoselective synthesis of conjugated dienes using air-stable potassium alkenyltrifluoroborates as coupling partners is described. The palladium-catalyzed cross-coupling reaction of potassium (E)- and (Z)-alkenyltrifluoroborates with either (E)- or (Z)-alkenyl bromides proceeds readily with moderate to excellent yields to give the corresponding (E,E)-, (E,Z)-, (Z,E)-, or (Z,Z)-conjugated dienes
描述了使用空气稳定的链烯基三氟硼酸钾作为偶联伴侣的立体选择性合成共轭二烯的方法。钯催化的(E)-和(Z)-烯基三氟硼酸钾与(E)-或(Z)-烯基溴化物的钯催化交叉偶联反应容易进行,产率中等至优异,得到相应的(E,E)- ,(E,Z)-,(Z,E)-或(Z,Z)共轭二烯立体定向。交叉耦合通常可使用5摩尔%的Pd(OAC)的实现2,10摩尔%的PPH 3和Cs的3当量2 CO 3在THF-H 2 O(10∶1)中。两种偶联伙伴均容许多种官能团。
Use of Samarium Diiodide as an Alternative to Sodium/Mercury Amalgam in the Julia-Lythgoe Olefination
作者:Gary E. Keck、Kenneth A. Savin、Michael A. Weglarz
DOI:10.1021/jo00115a041
日期:1995.5
Studies into the use of samarium diiodide (SmI2) in the reductive elimination of 1,2-acetoxy sulfones and the reductive cleavage of vinyl sulfones are reported. Parallel investigations with sodium/mercury amalgam (Na/Hg) revealed over-reduction in several cases in which the desired products were heavily conjugated or conjugated to an aromatic moiety. A mechanistic study revealed some of the intricacies of the SmI2-promoted Julia-Lythgoe olefination. The classical Na/Hg reductive method was also examined, and an alternative mechanism is proposed. Observations described herein provide important insights into the mechanism and synthetic utility of these methods. The optimum protocol developed utilizes SmI2 reduction of vinyl sulfones in the presence of DMPU and MeOH and gives generally high yields with good to excellent E stereoselectivity.
Conversion of allyl alcohols to dienes by sulfoxide and selenoxide syn elimination. Synthesis of PCB arene oxides
作者:Hans J. Reich、Ieva L. Reich、Susan Wollowitz
DOI:10.1021/ja00486a082
日期:1978.8
An E-selective 1,3-diene synthesis from moderated ylides and aldehydes
作者:E. Vedejs、Huang Wen Fang
DOI:10.1021/jo00175a057
日期:1984.1
Organoselenium chemistry. .alpha.-Lithio selenoxides and selenides. Preparation and further transformation to olefins, dienes, and allylic alcohols