Synthesis of Spiro 1,3-Oxazines via Three-Component Reaction of Conjugated Imines, Dialkyl Acetylenedicarboxylates and N,N'-Disubstituted Parabanic Acids

A series of structurally diverse spiro 1,3-oxazines were conveniently prepared from three-component reaction of conjugated imines, dialkyl acetylenedicarboxylates (DAAD), and N,N'-disubstituted parabanic acids in dry dichloromethane without catalyst. Initially, various conjugated imines were synthesized from reaction of aniline derivatives with cinnamaldehyde. Subsequently, reaction of conjugated imines with DAAD and N,N'-substituted parabanic acids led to mixture of the corresponding spirocyclic 1,3-oxazines in high yields. The obtained diastereoisomers of the spirocyclic 1,3-oxazines were isolated and characterized by FT-IR, ¹H, ¹³C NMR spectral data, elemental analyses and mass spectrometry.