Halogen‐Driven Chemospecific [3+2] Cycloaddition of Azomethine Ylides with Enals. Synthesis and Chemical Properties of 1‐(Halovinyl)‐2‐Aminoethanols

Abstract The investigation of the reactivity of nonstabilized N ‐alkylazomethine ylides with acroleins, substituted by chloro, bromo, or phenoxy group, reveals the chemospecific addition to C═O double bond furnishing the 5‐vinyloxazolidines. The latter are demethylenated by refluxing with hydrazine hydrate in ethanol to give ( Z )‐1‐(alkylamino)but‐3‐en‐2‐ols in 30%–100% yield. The subsequent research of the chemical properties of these aminobutenols demonstrates a diverse reactivity allowing the formation of 2,2‐disubsituted‐ N ‐methylethan‐1‐amines, 4‐styryl‐1,2,3,4‐tetrahydroisoquinolines or 2,3‐disubstituted pyrroles upon treatment with perchloric acid.