1,3-CYCLOADDITIONS TO HIGHLY SUBSTITUTED, STRAINED DOUBLE-BONDS - SPIRO-BETA-LACTAMS FROM ALPHA-METHYLIDENE-BETA-LACTAMS BY REACTIONS WITH DIPHENYLNITRILIMINE, ACETONITRILE OXIDE, NITRONES, AND DIAZOMETHANE

Substituted dihydropyrazole-spiro-beta-lactams and isoxazolidine-spiro -beta-lactam derivatives are regio-and stereoselectively prepared by 1 ,3-cycloadditions between substituted alpha-methylidene-beta-lactams a nd diazomethane, nitrones, or the in-situ-prepared dipoles 'diphenylni trilimine' and acetonitrile oxide. These reactions represent examples for 1,3-cycloadditions to the highly substituted, strained double bond s of alpha-methylidene-beta-lactams, and they need special experimenta l conditions as all reaction products are relatively unstable. Especia lly in solution, the reverse reaction is highly favoured. Regioselecti vity and stereoselectivity of the reactions are elucidated mainly by N MR techniques such as 2D-INEPT, ATP, and NOE experiments.