Diastereoselective Synthesis of Nine-Membered Heterocycles via the Cycloaddition and Sequential Rearrangement of N-Vinyl Nitrones with Isocyanates

摘要

A metal-free construction of highly diastereoselective nine-membered heterocycles is described via the cycloaddition and rearrangement of N-vinyl-alpha, beta-unsaturated ketonitrones and isocyanates. Notably, the prepared nine-membered heterocycles afforded 2,3-dihydropyrrolizines under heating conditions. Mechanistic studies showed that the nine-membered rings might undergo decarboxylation, isomerization, aza-Michael addition, and aromatization to afford 2,3-dihydropyrrolizines in a one-pot reaction.