Chemoselective and Diastereoselective Intramolecular (3+2) Cycloadditions of Epoxy and Aziridinyl Enolsilanes

Epoxy and aziridinyl enolsilanes react as oxyallylic cation equivalents in highly chemo- and diastereoselective intramolecular (3+2) cycloadditions with a range of dienes and olefins. With acyclic dienes, the (3+2) cycloaddition outcompetes the (4+3) pathway traditionally observed in this kind of system almost exclusively. With both conjugated dienes and isolated olefins, excellent diastereoselectivities are observed, and cycloadducts can be obtained in optically-enriched forms. Computational studies indicate that the stepwise (3+2) cycloaddition involves an activated epoxy/aziridinyl intermediate and the conformational flexibility of the intermediate determines the preference for (3+2) cycloadduct formation. Further transformations of the (3+2) cycloadducts produce densely functionalized trans-hydrindane scaffolds.

Automated summary

Epoxy and aziridinyl enolsilanes can react as oxyallylic cation equivalents in highly selective and stereoselective intramolecular (3+2) cycloadditions. Computational studies suggest that the stepwise reaction involves the conformational flexibility of the intermediate, which determines the formation of (3+2) cycloadducts. This method can be used for the synthesis of densely functionalized trans-hydrindane scaffolds.