Enantioselective Synthesis of cis-Decalin Derivatives by the Inverse-Electron-Demand Diels-Alder Reaction of 2-Pyrones.

A novel strategy for the synthesis of cis-decalins by an ytterbium-catalyzed asymmetric inverse-electron-demand Diels-Alder reaction of 2-pyrones and silyl cyclohexadienol ethers is reported here. A broad range of synthetically important cis-decalin derivatives with multiple contiguous stereogenic centers and functionalities are obtained in good yields and stereoselectivities. A full set of diastereomeric substituted cis-decalin motifs are readily accessible by tuning the absolute configurations of substituted silyl cyclohexadienol ethers (R or S) as well as the ligands (R or S). The synthetic potential is showcased by the enantioselective total synthesis of 4-amorphen-11-ol, and further demonstrated by the first total synthesis of cis-crotonin.