Intramolecular Hetero-Michael Addition of β-Hydroxyenones for the Preparation of Highly Substituted Tetrahydropyranones
作者:Maud Reiter、Hazel Turner、Véronique Gouverneur
DOI:10.1002/chem.200600415
日期:2006.9.18
6-endo-trig ring closure to form highly substituted tetrahydropyranones. Amberlyst-15, Al(ClO(4))(3) x 9 H(2)O and [Pd(MeCN)(4)](BF(4))(2) were found to be suitable catalysts for these intramolecular conjugate additions, preventing side reactions, such as dehydration or retroaldolisation. The use of [Pd(MeCN)(4)](BF(4))(2) is particularly effective, as this palladium-mediated reaction is under kinetic control
显示结构上不同的β-羟基烯酮经历非氧化的6-内-trig环闭合以形成高度取代的四氢吡喃酮。发现Amberlyst-15,Al(ClO(4))(3)x 9 H(2)O和[Pd(MeCN)(4)](BF(4))(2)是这些分子内共轭物的合适催化剂此外,还可以防止诸如脱水或逆醛缩醛反应等副反应。[Pd(MeCN)(4)](BF(4))(2)的使用特别有效,因为此钯介导的反应处于动力学控制之下,并产生具有高非对映异构控制水平的三取代和四取代的四氢吡喃酮。在路易斯酸Al(ClO(4))(3)x 9 H(2)O的存在下,该反应以相似的非对映体控制进行。但是,与[Pd(MeCN)(4)](BF(4))(2)相比,该催化剂可以促进烯醇化。还发现钯介导的反应与富含对映体的β-羟基烯酮底物相容,闭环时不损失对映体纯度。从这种新化学中出现的最独特的合成发展是可以从反醛醇前体中获得三和四取代的2,6-抗四氢吡喃酮