Background: Azlactones, also known as oxazolones, are a class of versatile intermediates
and are commonly used for the synthesis of various heterocyclic scaffolds and unnatural α-amino acids.
In particular, because of their inherent multiple sites of reactivity, azlactones have recently attracted a
great deal of research efforts from the synthetic community. By exploring different sites of reactivity, a
variety of cycloaddition reactions have been developed to construct diverse synthetically and biologically
important hetereocycles as well as α-amino acid derivatives bearing quaternary carbons. With the development
of asymmetric catalysis, a range of catalytic asymmetric variants have also been developed
by metal and organocatalysis to access various valuable enantioenriched molecules. However, to the
best of our knowledge, there is still no comprehensive review devoted to this emerging topic to date.
Methods: We performed a systemic survey of azlactone-mediated cycloaddition reactions by SciFinder
search. To calibrate the reasonable scope of this survey, we highlight the recent advances in the field of
cycloaddition reactions of azlactones, and their applications to the construction of heterocycles according
to the different types of reaction modes. Thus, thirty four leading papers were included in this review
and accordingly organized by different sites of reactivity, including [2+3], [2+4], [2+8], and [3+2]
Conclusion: The results shown in this review confirmed the significance of such type of versatile intermediates.
The discovery of new suitable reactive species and application of other catalytic modes can
provide a fruitful platform for the development of new cycloadditions of azlactones.