Utilization of the Intramolecular Cycloaddition−Cationic π-Cyclization of an Isomünchnone Derivative for the Synthesis of (±)-Lycopodine
作者:Albert Padwa、Michael A. Brodney、Joseph P. Marino、Scott M. Sheehan
DOI:10.1021/jo960829p
日期:1997.1.1
chloride in the presence of chlorotrimethylsilane. Ozonolysis of the resulting silyl enol ether followed by a Wittig reaction and conversion to the desired alpha-diazo imide was carried out using standard malonylacylation and diazotization procedures. Treatment of the alpha-diazo imide with rhodium(II) perfluorobutyrate afforded a transient 1,3-dipole which subsequently cycloadded across the tethered pi-bond
通过使用异麦草酮偶极的串联环加成-阳离子pi环化反应作为关键的战略要素,可以实现一个新的环化序列,从而产生生物碱Lycopodium家族的四环骨架。所需的α-重氮酰亚胺前体的合成涉及在氯代三甲基硅烷存在下,用衍生自3-甲氧基苄基氯的有机铜试剂处理5-甲基环己基-2-烯-1-酮。使用标准的丙二酰基酰化和重氮化程序进行所得甲硅烷基烯醇醚的臭氧分解,然后进行维蒂希反应并转化为所需的α-重氮酰亚胺。用全氟丁酸铑(II)处理α-重氮酰亚胺可得到一个瞬态的1,3-偶极子,随后通过束缚的π键进行环加成。所得的环加合物用BF(3)处理。2AcOH得到由N-酰基酰亚胺离子的Pictet-Spengler型环化衍生的重排四环化合物。随后将重排的产物转化为先前用于合成(+/-)-番茄红素的关键中间体。