Efficient Allylation of Aldehydes Promoted by Carboxylic Acids
作者:Gui-long Li、Gang Zhao
DOI:10.1021/jo050186q
日期:2005.5.1
mediating the allylation of aldehydes with allytributyltin in different solvents. A novel, general, and practical method of allylation of aldehydes promoted by carboxylic acids under mild reaction conditions has been developed. Among them, p-nitrobenzoic acid afforded high to quantitative yields of the homoallylicalcohol products, and can be easily recovered after workup by aqueous HCl. Glyoxylic
已经筛选出各种羧酸以在不同溶剂中介导醛与烯丙基三丁基锡的烯丙基化。已经开发了在温和的反应条件下烯丙基化由羧酸促进的醛的新颖,通用和实用的方法。其中,对硝基苯甲酸提供了高至定量产率的均烯丙基醇产物,并且在用HCl水溶液处理后可以容易地回收。乙醛酸自催化烯丙基化,而无需添加任何其他助催化剂或催化剂,从而以高收率得到相应的烯丙基化产物。通过控制羧酸的酸度,可以调节醛的丁酰化的区域选择性。醛的crotylation生产的α-加合物作为主要产物,使用CF可以中等至良好的收率3 CO 2 H作为促进剂。还讨论了烯丙基化的可能机制。
Allylation of Aldehydes Promoted by the Cerium(III) Chloride Heptahydrate/Sodium Iodide System: the Dependence of Regio- and Stereocontrol on the Reaction Conditions
The cerium(III) chloride heptahydrate/sodium iodide complex (CeCl3 ⋅ 7 H2O/NaI) acts as a useful promoter in the carbon-carbonbond forming reaction by addition of allyltributylstannanes to aldehydes. The reaction of 2-butenyltributylstannane shows that the regio- and the stereochemical outcomes depend on the reaction conditions. When the promoter is adsorbed on a solid support (aluminum oxide), a
铈(III)七水合氯化/碘化钠复合物(加入CeCl 3 ⋅7 H 2 O / NAI)作为在碳-碳键形成通过加入allyltributylstannanes醛的反应的有用的启动子。2-丁烯基三丁基锡烷的反应表明区域和立体化学结果取决于反应条件。当促进剂吸附在固体载体(氧化铝)上时,在无溶剂条件下会观察到非常普遍的γ加合物形成。相反,当反应在乙腈作为溶剂中进行时,α-加合物占优势。在最后一种情况下,观察到完全的立体控制,以高几何纯度获得较不稳定的(Z)-异构体。
Crotylation of Aldehydes by Crotyltins: Discrimination between Mechanisms Involving Transmetallation or Simple Lewis Acid Assistance through the Consideration of the Stereochemistry of the Corresponding Homoallylic Alcohols
In the reaction of crotyltins with aldehydes in the presence of metal salts, the double consideration of the syn/anti ratio of the branched homoallylicalcohols and the Z/E ratio of their linear regioisomers is proposed as a way to discriminate between a reaction mechanism involving a transmetallation step and a reaction mechanism involving simple Lewis acid activation of the aldehyde. The formation