Single-Electron/Pericyclic Cascade for the Synthesis of Dienes

The highly efficient and diastereoselective synthesis of E dienes has been accomplished through radical cyclization of bromoallyl hydrazones. This methodology has been further extended to generate these products through a one-pot condensation/radical cyclization/cycloreversion cascade from simple aldehyde starting materials in high yields (> 75%) and high diastereoselectivities (> 95: 5). Mechanistic investigations suggest that the cascade reaction proceeds through a cyclic diazene intermediate prior to the cycloreversion.