Addition of the Reformatskii reagent to azirines. Synthesis of 4-amino lactones.
Résumé
Reformatskii reaction of α-bromoesters with azirines gave 2 diastereomeric compds. which cyclized by reaction with Olah's reagent (HF/pyridine) to give amino lactones. E.g., Reformatskii reaction of the azirine I with MeCHBrCO2Et gave a mixt. of II (R = H, R1 = Me; R = Me, R1 = H), in a ratio of 10:90, resp. Cyclization of the isomeric mixt. with Olah's reagent gave the amino lactones III (R = H, R1 = Me; R = Me, R1 = H, resp.). The stereochem. of the azirine ring-opening and the mechanism of reaction is discussed. [on SciFinder(R)]