Oxazolones in organocatalysis, new tricks for an old reagent

Oxazolones or azlactones are among the most-common starting materials for the synthesis of quaternary amino acids. Since the seminal works of Steglich and co-workers until the recent examples from Ooi and co-workers, azlactones have been the focus of intense research. Oxazolones are also widely used in organometallic chemistry; however, with the "renaissance" of organocatalysis, this reagent has emerged as an important starting material for a broad range of new organocatalytic asymmetric methodologies. In this Focus Review, we aim to cover all of these new organocatalytic methodologies. We begin by discussing the dynamic kinetic resolution reactions developed with azlactones. Then, we disclose the organocatalytic rearrangements. Finally, we focus on the use of oxazolones as nucleophiles in organocatalytic processes.