Synthesis and x-ray crystal structure analysis of substituted-2,3-dihydro-1,3,4-oxadiazoles via reaction of acetone-and cycloalkanone benzoylhydrazones with phenylisocyanate

Abstract EN

Acetone and cycloalkanones benzoylhydrazones (1a-f) react readily with phenyl isocyanate 2 at room temperature to give the corresponding dimethyl- and spiro-substituted 2, 3-dihydro-1, 3, 4-oxadiazoles (3a-f), respectively.

Structure elucidation of these compounds was based on spectral data and confirmed by X-ray crystal structure analysis for compound 3d.

Treatment of 3 with trifluoroacetic anhydride resulted in the formation of the acyclic adduct 2, 5-dioxo-1, 5-diphenyl- 1, 3, 4-triazapentane 5 via elimination of the respective alkene in moderate yields.