Tandem Claisen Condensation/Transesterification between Arylacetate Enolates and Arylmethylene-Substituted 2,2-Dimethyl-1,3-dioxolan-4-ones: An Improved Synthesis of <i>Z</i>-Configured Pulvinones
作者:Reinhard Brückner、Natasza Kaczybura
DOI:10.1055/s-2006-950378
日期:2007.1
Horner-Wadsworth-Emmons (HWE) alkenations of aromatic aldehydes with the novel phosphonate 24b led to E-configured arylmethylene-substituted 2,2-dimethyl-1,3-dioxolan-4-ones 25a-f (79-88% yield). The latter condensed with the lithium enolates of methyl arylacetates lithio-20b-d to give, after acid treatment and crystallization, isomerically pure (Z)-pulvinones 8d-s in 75-91% yield. We also showed that Horner-Wadsworth-Emmons reactions between phosphonate 24b and aliphatic aldehydes lead to E-configured alkylmethylene-substituted 2,2-dimethyl-1,3-dioxolan-4-ones 25g-i (82-96% yield).