结果表明,可以通过两步法从庚二烯-4,5-二羧酸酯中得到相应的邻二甲基乙醇2并用MnO 2或IBX进行还原和氧化脱氢制得的heptaleno [1,2- c ]呋喃1(方案4),在呋喃环上的Diels–Alder型[4 + 2]环加成反应中与许多缺电子的双极性亲热物发生热反应,生成相应的1,4-环氧苯并[ d ]庚烷(参见方案6、15、17 ,和19)。乙炔二甲酸二甲酯(ADM)与1根引线之间的热反应通过动力学控制从空间上不太拥挤的过渡态(图4)到形成(M *)构型的1,4-二氢-1,4-环氧苯并[ a ]庚烷,其经历了向能量上循环的双键转移较宽松的苯并[ d ]庚烷4(方案6和7)。后者的大多数在热条件下在手性轴上显示差向异构,因此在反应混合物中发现(M *)-和(P *)-立体异构体。(P *)构型的4在热平衡实验中受到青睐,与AM1计算一致(表1)。)。苯并[ d ]庚二烯-2,3-
A novel approach towards the synthesis of functionalized benzo[a]heptalenes 9 and 10 via a 6 6pi-electrocyclic ring closure - aromatization sequence of corresponding bis[prop-2-enoates] 5 and 6 has been developed (Scheme 1). The starting bis[prop-2-enoates] have been prepared from the corresponding dialdehydes 3a and 4a in a Wittig-Horner reaction, and their UV/VIS properties have also been investigated (Fig. I and Table 1). The dehydrogenations of the corresponding diols I and 2 to dialdehydes with a number of oxidizing reagents, including MnO2 in CH2Cl2, tetrapropylammonium perruthenate (TPAP), and activated DMSO, have been studied in detail.