The Sakai aryl aldehyde – cyclic ketone aldol – Grob fragmentation sequence was extended to cinnamaldehyde and cyclohexanone, and the product was elaborated to analogues of the alkaloid piperstachine. The effects of substituents on the reaction involving cinnamaldehyde were studied. The aldol-fragmentation sequence failed with benzaldehyde when cyclooctanone or cyclobutanone was substituted for cyclohexanone or cyclopentanone, and the reasons for this failure were examined. Four-carbon Wittig homologation of the piperonal–cyclobutanone aldol-fragmentation product, a hypothetical route to alkaloids such as retrofractamide A, was thus not viable. Instead, three-carbon homologation of the readily available piperonal–cyclopentanone product, using alkyne chemistry recently disclosed by Lu and Trost, afforded these alkaloids in excellent overall yield. The alkyne isomerization was also used to effect efficient syntheses of pellitorine and several other non-aromatic 2E,4E-dienoic Piper amide alkaloids. Key words: Piper, amides, alkaloids, insecticides, aldol, fragmentation, cinnamaldehydes, alkyne, redox, isomerization.
Sakai芳基醛-环酮Aldol-Grob断裂序列被扩展到肉桂醛和环己酮,并将产物改造为吡啶碱类似物。研究了涉及肉桂醛的反应中取代基的影响。当环辛酮或环丁酮替代环己酮或环戊酮时,苯甲醛无法进行Aldol-断裂序列,对此失败的原因进行了研究。对吡哆醛-环丁酮Aldol-断裂产物进行了四碳Wittig同系化,这是通往碱类如retrofractamide A的假设路线,但该方法并不可行。相反,利用Lu和Trost最近披露的炔化学,对易得的吡哆醛-环戊酮产物进行了三碳同系化,以极高的总产率制备了这些碱类。炔异构化还被用于高效合成辣椒碱和几种其他非芳香2E,4E-二烯酸Piper酰胺类碱类。关键词:Piper、酰胺、碱类、杀虫剂、Aldol、断裂、肉桂醛、炔、氧化还原、异构化。