Chemoselective and Diastereoselective Intramolecular (3+2) Cycloadditions of Epoxy and Aziridinyl Enolsilanes
Yueyao Chen, Jesse Ling, Angus B. Keto, Yun He, Kam‐Hung Low, Elizabeth H. Krenske, Pauline Chiu
Abstract
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.