A facile access to spiro furanone skeleton based on Pd(II)-mediated cyclization–carbonylation of propargylic esters
作者:Keisuke Kato、Hideaki Nouchi、Keisuke Ishikura、Satoshi Takaishi、Satoshi Motodate、Hikaru Tanaka、Kazuho Okudaira、Tomoyuki Mochida、Ryuichiro Nishigaki、Koki Shigenobu、Hiroyuki Akita
DOI:10.1016/j.tet.2005.12.033
日期:2006.3
mediated by Pd(II) afforded cyclic orthoesters, which were hydrolyzed into γ-acetoxy-β-ketoesters. Based on the NMR experiments, it was presumed that the cyclization reaction was initiated by a nucleophilic attack of carbonyl oxygen to the alkyne carbon coordinated to palladium(II). When the γ-acetoxy-β-ketoesters were treated with a basic condition, Knoevenagel–Claisen type condensation took place, and
Pd(II)介导的炔丙基酯的氧化环化-羰基化反应生成环状原酸酯,然后将其水解为γ-乙酰氧基-β-酮酸酯。基于NMR实验,推测环化反应是由羰基氧对配位于钯(II)的炔碳的亲核攻击引发的。在碱性条件下处理γ-乙酰氧基-β-酮酸酯时,发生了Knoevenagel–Claisen型缩合反应,并以高收率获得了螺呋喃酮衍生物。我们将这些反应应用于类固醇衍生物,并合成了具有螺呋喃酮片段的类固醇衍生物。其中,螺呋喃酮4j具有血管舒张活性和心动过缓。化合物2i – 4k 对CYP3A有抑制作用。