Single and double ring closing metathesis in the formation of dihydropyrans and bisoxacyclic systems with a quaternary centre
作者:Bernd Schmidt、Holger Wildemann
DOI:10.1039/b004302h
日期:——
Starting from α-hydroxy carboxylic acid esters, allyl homoallyl ethers with a quaternary centre become available in a one-pot reaction via a sequence of O-allylation–Wittig-rearrangement–O-allylation. Elaboration of the side chain provides various precursors for dihydropyrans and bisoxacyclic systems, which become available by single or double ring closing metathesis. Double ring closing metathesis of the substrates investigated in this study is highly regioselective to give dihydropyrans linked via a C–C-bond to a dihydrofuran or an oxepine. The regioisomeric fused products are not formed in the reaction.
以α-羟基羧酸酯为起点,通过O-烯丙基化-维蒂希-重排-O-烯丙基化的顺序,烯丙基均烯丙基醚在一次反应中就能得到具有季中心的烯丙基均烯丙基醚。侧链的细化为二氢吡喃和双氧杂环系统提供了各种前体,这些前体可通过单环或双环闭合偏析反应获得。本研究中研究的底物的双关环化反应具有高度的区域选择性,可以得到通过 C-C 键与二氢呋喃或氧杂环庚烷连接的二氢吡喃。反应中不会形成隶属异构的融合产物。