A stereospecific synthesis of oxazolinyloxiranes

Lithiooxiranes 3a and 3b, generated by deprotonation of oxiranes 2a and 2b with s-BuLi at - 100 degreesC in Et2O, were found to be chemically very sta ble. trans-Lithiooxirane 3a was also configurationally stable and reacted s tereospecifically with electrophiles to give 4a-k. In contrast, cis-lithioo xirane 3b was found to be configurationally much less stable and reacted wi th electrophiles affording mixtures of diastereomers 4, 7, and 8, After onl y a very short reaction time, 3b too reacted with electrophiles highly ster eospecifically. Deprotonation-deuteration and deprotonation-alkylation of c hiral oxazolinyloxiranes 12a and 12b to give oxiranes 12c and 12d were also examined. Semiempirical and ab initio calculations were carried out in an effort to explain the observed stereochemistry.