Sr. Martel et al., THE AZOMETHINE YLIDE STRATEGY FOR BETA-LACTAM SYNTHESIS - THE STRUCTURE OF THE KEY 1,3-DIPOLAR INTERMEDIATE, Chemical communications, (19), 1997, pp. 1897-1898
The thermolysis of the beta-lactam-based oxazolidinone 1 leads to the
formation of cycloadducts 2 and evidence is presented for the particip
ation of the carboxylated azomethine ylide 4, rather than 3 (the more
conventional product of oxazolidinone fragmentation), as the key 1,3-d
ipolar intermediate in this process.