Azetidin-2-one, a four-membered cyclic lactam (beta-lactam) skeleton has been recognised as a useful building block for the synthesis of a large number of organic molecules by exploiting the strain energy associated with it, in addition to its use in the synthesis of a variety of beta-lactam antibiotics. Efforts have been made in exploring such new aspects of beta-lactam chemistry using enantiomerically pure beta-lactams as versatile intermediates for the synthesis of aromatic beta-amino acids and their derivatives, peptides, polyamines, polyamino alcohols, amino sugars and polyamino ethers. The development of methodologies based on beta-lactam nucleus is now referred as 'the beta-lactam synthon methods'. The selective bond cleavage of the strained ring coupled with further interesting transformation render this fascinating molecule as a powerful building block. This provides an access to diverse structural type of synthetic target molecules lacking beta-lactam ring structure. This review provides an account of synthesis of organic compounds having biological significance at the same time lacking beta-lactam ring, by using beta-lactam as synthon.

ortho-Palladated aryl oxime and amines with a N-heterocyclic carbene ligand show increased thermal stability and catalyze the Mizoroki-Heck and Suzuki reaction with high yields, and moderate TON (2,000-92,000) and TOF (200-4,300 h -1 ). Homo coupling of the aryl halides gave low yields of the biaryls in the presence of these catalysts.

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The HOPO vinyl sulfonamide 3 and the corresponding HOPO acrylamide 10, were easily prepared by short synthetic sequences. Investigation of the aza-Michael reactions of these linkers showed that they proceed at a higher rate in solvent systems containing water. The scope and limits of the aza-Michael reactions of 3 and 10 were examined. Reagents 3 and 10 reacted cleanly with piperazine to give the corresponding adducts which were deprotected to give the di-HOPO ligands 7 and 16. Reaction of HOPO acrylamide 10 with 1,4,7-triazacyclononane gave the tris-adduct 17 which was deprotected to give the desired tris-HOPO ligand 18. Overall, the aza-Michael reactions of 3 and 10 appear to be governed not only by the solvent but also by the nature of the amine and the solubility of the reaction intermediates.