Novel Heterocycles by Bis Heteroannulation of Oxazoles

Article abstract of DOI:10.1021/jo00010a044

We report the first examples of intramolecular Diels-Alder addition of heterodienophiles N=N, C=N, C=O, C=S to oxazoles.The required 5-ethoxy- and 5-phenyloxazoles were synthesized bearing a side chain of variable length on C-2 to which the different heterodienophiles are attached.The products of the thermal bis heteroannulation are 3-triazolines, imidazolines, oxazolines, or thiazolines fused to a five- to six-membered ring.Relative reactivities were established and the mechanism is discussed.