SYNTHESIS OF PYRROLIZIDINES AND INDOLIZIDINES BY THE INTRAMOLECULAR CYCLOADDITION OF AZIDES WITH ELECTRON-RICH 1,3-DIENES - A SYNTHETIC EQUIVALENT OF A NITRENE DIENE CYCLOADDITION

Alkyl azides were found to undergo intramolecular cycloadditions with certain 1,3-dienes to provide 2,3,5,7a-tetrahydro-1H-pyrrolizines and 3,5,6,7,8,8a-hexahydroindolizines in one operation (e.g., 12 →13 and 17 →18). The presence of an electron-donating group on the diene (sulfur, selenium, or oxygen) was required to avoid alternative rearrangement processes. The cyclization of chiral azidodienes proceeded with high diaster-eoselectivity to produce materials that are closely related to several alkaloidal natural products. New methods for the synthesis of the requisite heterosubstituted 1,3-dienes were developed. © 1990, American Chemical Society. All rights reserved.