Aza-[3,3]-Claisen Enolate Rearrangement in Vinylaziridines: Stereoselective Synthesis of Mono-, Di-, and Trisubstituted Seven-Membered Lactams

Several 2,3-disubstituted vinylaziridines have been N-acylated and subjected to LiHMDS in THF at -78 degrees C. Upon warming to room temperature, the resulting amide enolates underwent a highly stereoselective [3,3]-sigmatropic rearrangement to give mono-, di-, and trisubstituted seven-membered lactams in good yields. The scope and limitations of the process have been investigated by using variously substituted vinylaziridines. A kinetically controlled process proceeding through a six-membered boatlike transition state assembly has been invoked to explain the stereochemical outcome of the reaction.