I. Palladium-catalyzed tandem dehydrogenation and oxidative heck reaction of β-Heteroatom-Substituted ketones II. Studies toward the synthesis of compounds with α-Methylene-γ-lactone core structure

Abstract

Cyclic enolone and enaminone derivatives are considered as important scaffolds due to their synthetic utility and biological activities. Therefore, we developed an approach to functionalized cyclic enolone and enaminone derivatives from simple saturated $\beta$-heteroatom-substituted ketones in one-pot. Palladium-catalyzed tandem dehydrogenation and oxidative Heck reaction on the 4-chromanone and N-acetyl-4-piperidone was successfully conducted and the desired C3-vinyl products were obtained in fair to good yield. Observation of reaction profile suggested the intermediacy of chromone in this reaction sequence. Furthermore, two-step synthesis of 2,3-bifunctionalized chromone series was efficiently progressed by applying the newly developed tandem reaction. Synthetic route for $\alpha$-methylene-$\gamma$-butyrolactone scaffolds which is common core structure in diverse bioactive natural products was investigated. Retrosynthetic analysis suggested that iodolactonization, catalytic hydrogenation and Horner-Wadsworth-Emmons reaction might be the key step in this synthetic pathway to the bicyclic $\alpha$-methylene-$\gamma$-butyrolactones with amino group.