A Stereoconvergent Intramolecular Diels–Alder Cycloaddition Related to the Construction of the Decalin Core of neo-Clerodane Diterpenoids

Several examples of a highly specific, stereoconvergent intramolecular Diels–Alder cycloaddition that led to the trans-decalin core of neo-clerodane diterpenoids are described. The relative configuration adjacent to the dienophile, which led to C4 of the decalin system, as well as the electron-withdrawing effects of various substituents and conformational rigidity of the Diels–Alder precursors were explored.