STEREOSELECTIVE SYNTHESIS OF alpha-METHYLENE-gamma-BUTYROLACTAMS FROM ETHYL 2-(BROMOMETHYL)ACRYLATE AND CHIRAL SULFINYL ALDIMINES MEDIATED BY INDIUM

The reaction of ethyl 2-(bromomethyl)acrylate (1) with chiral N-tert-butylsulfinyl aldimines 2 and indium powder in THF at 100 degrees C for 48 h affords, after hydrolysis, a mixture of N-tert-butylsulfinyl aminoesters 3 and alpha-methylene-gamma-butyrolactams 4. From the reaction mixture, compounds 3 were quantitatively converted to the expected butyrolactams 4 after removal of the tert-butylsulfinyl group under acidic conditions and final basic workup. The whole process takes place in high overall yields and with fairly good stereoselectivities.