Palladium-Catalyzed Asymmetric Allylic Alkylation of Cyclic Dienol Carbonates: Efficient Route to Enantioenriched γ-Butenolides Bearing an All-Carbon α-Quaternary Stereogenic Center
Allyl dienol carbonates (1) served as substrates for the title reaction to afford the furanones 2 in both high yields and high enantioselectivities. These furanones were eventually converted into valuable buildingblocks including γ‐tertiary and γ‐quaternary furanones (3) as well as β‐quaternary butyrolactones (4). This method was used as a key step in the totalsynthesis of (−)‐nephrosteranic acid
substituted furans by a one‐pot four‐step sequence featuring a palladium‐catalyzed decarboxylative allylic alkylation, a microwave‐mediated Cope rearrangement, a nucleophilic addition, and a dehydration reaction (see scheme). The protocol is operationally simple, highly flexible, and provides di‐, tri‐, and tetrasubstituted furans starting from readily available materials.