A Novel Access to γ-Alkylidenebutenolides: Sequential Stille Couplings of Dibromomethylenebutenolides
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 mono-bromobutenolides with excellent stereo- and regiocontrol. A second Stille coupling or the reduction with Zn dust led to bromine-free γ-alkylidenebutenolides as single stereoisomers.
Sorg, Achim,Siegel, Konrad,Bru?ckner, Reinhard
p. 321 - 325
(2007/10/03)
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