developed by inverse-electron-demand oxa-Diels–Alder reaction of α-keto-β,γ-unsaturated esters with α,β-unsaturated hydrazones as electron-rich olefins. This reaction is catalyzed by Eu(hfc)3 and proceeds in an endo-selective manner. This umpolung cycloaddition affords a variety of substituted dihydropyrans stereoselectively in high yields. In addition, indirect synthesis of formyl-substituted dihydropyran
通过逆电子需氧-α-酮,β,γ-不饱和酯与α,β-不饱和为富电子烯烃的反电子要求的oxa-Diels-Alder反应,开发了一种简明的二氢
吡喃合成方法。该反应被Eu(hfc)3催化并以内选择性的方式进行。该化合物环加成以高产率立体选择性地提供了多种取代的二氢
吡喃。另外,通过环加合物的脱
水偶氮反应实现了甲酰基取代的二氢
吡喃的间接合成。预期该方法可用于合成具有不同取代模式的二氢
吡喃和
四氢吡喃。