Versatile synthesis of quaternary 1,3-oxazolidine-2,4-diones and their use in the preparation of α-hydroxyamides

A new approach to the synthesis of 1,3-oxazolidine-2,4-diones, via a two-step reaction sequence, starting from the readily available α-ketols and isocyanates, is reported. The condensation of the latter led to the key precursors 4-methylene-2-oxazolidinones, which are converted into the diones by an oxidative cleavage of the exocyclic double bond. Thus, 5,5-disubstituted 1,3-oxazolidine-2,4-diones can be accessed in good yields from the appropriate functionalized α-ketols. Moreover, two alternative routes are also described either by functionalization of 4-oxazolin-2-ones or by alkylation of the 1,3-oxazolidine-2,4-dione core previously prepared. Upon hydrolysis of the 1,3-oxazolidine-2,4-diones, a series of α-hydroxyamides bearing a quaternary stereocenter were obtained.