2-(3H)-Oxazolone - A Simple Heterocycle with Manifold Potential

The simple heterocycle 2-(3H)-oxazolone has long proven itself a versatile tool in the hands of the synthetic organic chemist. Its numerous derivatives have served in many roles - from activating groups in coupling reactions, to efficient and reliable chiral auxiliaries, as focal points for asymmetric catalysis, or more recently as a versatile synthon in target-oriented synthesis. Although several obvious comparisons are prone to arise, in particular with the structurally related yet more celebrated oxazolidinones, the extensive use of the latter are beyond the scope of this work. Instead, the purpose of this review is to highlight some of the broader capabilities of oxazolone itself, indeed many of which we feel are underutilized as of yet. Wherever relevant, comparison with analogous heterocyclic species will be presented. Specific areas under consideration will include: synthesis and simple derivatization, including N- and O- alkylations and acylations; reactivity of the parent heterocycle in processes involving the pi-system, such as electrophilic addition, radical reactions, cycloadditions and so on, in both inter- and intramolecular fashion; operation of the oxazolone framework in development and utilization of novel asymmetric processes In addition, the direct incorporation and manipulation of the oxazolone framework as a valuable synthon in target-oriented synthesis, in particular toward a variety of alkaloid systems, will be covered as appropriate.