Microwave-Assisted Improved Synthesis of Oxazolidin-2-ones, Oxazolidine-2-thiones and Thiazolidine-2-thione Chiral Auxiliaries

A microwave assisted method for the synthesis of some typical 4-substituted oxazolidinone chiral auxiliaries used in asymmetric synthesis is reported in this work. Under these conditions, treatment of (S)-phenylalaninol, (S)-phenylglycinol, (S)-valinol and (1S, 2R)-norephedrine with ethyl carbonate or carbon disulfide under the appropriate and specific microwave reaction conditions, led to an efficient synthesis of some oxazolidin-2-ones, oxazolidine-2-thiones and thiazolidine-2-thiones. The methodology reported in this paper provides these chiral auxiliaries with improved yields and a remarkable reduction on the reaction times, particularly in the case of thiazolidine-2-thiones, as compared with the conventional methods. All the auxiliaries prepared here show spectroscopic data in full agreement with those previously reported in the literature.