MESOIONIC OXAZOLONES .9. THEORETICAL-STUDY ON THE PROTONATION OF NONACYLATED AND ACYLATED COMPOUNDS

The PM3-computed structural transformations due to the protonation of some non-acylated and acylated bicyclic mesoionic oxazolones were anal ysed in terms of re-hybridization and x-bond orders variations. Accord ing to the calculated heats of formation, the non-acylated derivatives underwent protonation at their C-4 carbon atom, in agreement with exp erimental evidences, For the acylated compounds, the experimentally pr oved competition between acyl oxygen (O-13) and carbon atoms as sites of protonation was only in part confirmed.