[3-C AND C-N BOND-CLEAVAGE(2]CYCLOADDITION AND NUCLEOPHILIC ADDITIONSOF AZIRIDINES UNDER C)

Under PET conditions (photoinduced electron transfer) aziridines react with dipolarophiles in a [3+2] cycloaddition to form five-membered he terocycles. In this study we, used mono- and disubstituted N-alkyl and N-arylaziridines. We noticed that the radical cation as intermediate reacts in a different manner to the classical azomethine ylide. Furthe rmore, under mild thermal conditions, aziridines react in acetonitrile in a formal [3+2] cycloaddition with activated acetylene derivatives under C-N bond cleavage. Using methanol as solvent, the intermediate i s trapped leading to highly substituted enamines. A mechanism for this unexpected thermal reaction is proposed. (C) 1997 Elsevier Science Lt d.