Applications fused oxazole derivatives

Rather, the intent of the current project is to provide the reader with a discussion and leading examples of significant advances made in the synthesis, reactions, and applications of mononuclear oxazoles, oxazolones, oxazolines, and chiral bis(oxazolines) during this time frame. The material focuses on the more recent literature, although an update of the older synthetic literature is included wherever possible. In an effort to be selective, references to relevant reviews of material, not discussed in a chapter, are provided. Completely reduced oxazoles, that is, oxazolidines as well as benzo-fused derivatives, are outside the scope of this review. 

Numerous applications of IR spectral data have been reported for derivatives of (5,5)-fused ring systems, especially in connection with the problem of tautomeric equilibria. For example, the IR spectra of 5,6,7,8-tetrahydro-l//,3H-pyrrolo[l,2-c][l,3]oxazole-1,3-diones (24 X=0) and corresponding thiazole-l,3-diones (24 X = S) show no carbonyl absorption, but broad bands at 3300 cm-1 due to the associated OH group, indicating that the fused structures (24) exist in the enolic forms rather than their diketonic tautomers (81BJC1844). 

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