A Novel Access to γ-Alkylidenebutenolides: Sequential Stille Couplings of Dibromomethylenebutenolides
作者:Reinhard Brückner、Achim Sorg、Konrad Siegel
DOI:10.1055/s-2003-44997
日期:——
γ-(Dibromomethylene)butenolide (2) and β-bromo-γ-(bromomethylene)butenolide (Z-5), both of which obtained from dibromolevulinic acid (6) in a single step, underwent Pd-catalyzed couplings with phenyl- or styryltributylstannane giving monobromobutenolides with excellent stereo- and regiocontrol. A second Stille coupling or the reduction with Zn dust led to bromine-free γ-alkylidenebutenolides as single stereoisomers.
δ-(二溴亚甲基)丁烯内酯(2)和δ-²-溴-δ-(溴亚甲基)丁烯内酯(Z-5)均由二溴乙酰丙酸(6)一步制得,它们在 Pd 催化下与苯基或苯乙烯基三丁基锡烷发生偶联反应,得到具有极佳立体和区域控制的单溴丁烯内酯。通过第二次 Stille 偶联或与 Zn 粉尘的还原反应,可得到不含溴的δ-亚烷基丁烯酸单立体异构体。