NOVEL DEHYDROGENATION OF 2,5-DIARYLSUBSTITUTED Δ2-OXAZOLINES TO OXAZOLES

Article abstract of DOI:10.1135/cccc19931631

The dehydrogenation of various 2,5-diaryl substituted Δ²-oxazolines with either Br2/LiBr/CaCO3 (molar ratio 1.05 : 2 : 3) or CuBr2/LiBrCaCO3 (2 : 1 :3) in refluxing o-dichlorobenzene gives the corresponding oxazole in up to 87percent yield.Free radical benzylic bromination followed by dehydrobromination is the expected dehydrogenation mechanism.The successful application of the reagent combination for this transformation is in contrast to standard dehydrogenation reagents, including N-bromosuccinimide, 2,3-dichloro-5,6-dicyano-1,4-benzoquinone, chloranil, NiO2 and active γ-MnO2.