作者:Jens Christoffers、Heiko Oertling、Wolfgang Frey
DOI:10.1002/ejoc.200300009
日期:2003.5
Monocyclic spiroannulation precursors 3a−c were obtained by Michael reactions of α-acetyl lactones 6a−c with methyl vinyl ketone (7). The selective formation of either regioisomer of both β-oxo (5a−c) and δ-oxo (4a−c) lactones from 3a−c was achieved by varying the reaction conditions. The δ-oxo lactones 4a−c were obtained under basic (buffered) conditions in a pyrrolidine/AcOH system. Under acidic
单环螺环化前体 3a-c 是通过 α-乙酰内酯 6a-c 与甲基乙烯基酮的迈克尔反应获得的 (7)。通过改变反应条件,从 3a-c 中选择性形成 β-氧代(5a-c)和 δ-氧代(4a-c)内酯的任一区域异构体。δ-氧代内酯 4a-c 在碱性(缓冲)条件下在吡咯烷/AcOH 系统中获得。在酸性条件下,环化反应得到 β-氧代内酯 5a-c。通过与通过皂化/脱羧直接衍生自 δ-氧代内酯 4b 和 4c 的醇 10b、c 的光谱相比,副产物 8b、c 被确定为 β-氧代内酯 5b 和 5c 的分解产物。(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)