title: Efficient entry to highly functionalized beta-lactams by regio- and stereoselective 1,3-dipolar cycloaddition reaction of 2-azetidinone-tethered nitrones. Synthetic applications.
abstract: Racemic as well as optically pure 2-azetidinone-tethered nitrones, both cyclic and acyclic, were smoothly prepared from 4-oxoazetidine-2-carbaldehydes. The regio- and diastereoselectivities of the intermolecular 1,3-dipolar cycloaddition reactions of 2-azetidinone-tethered nitrones with substituted alkenes and alkynes were investigated. 2-Azetidinone-tethered nitrones on reacting with various dipolarophiles yielded isoxazolinyl-, isoxazolidinyl-, or fused polycyclic-beta-lactams, exhibiting good regio- and facial stereoselectivity in the most of the cases. In addition, some interesting transformations of these cycloadducts were performed, yielding aziridinyl beta-lactams or functionalized beta-alkoxycarbonyl gamma-lactams (derivatives of the aza analogue of paraconic acid).
mesh_terms: D001384:Azetidines / Q000138:chemical synthesis*; D020650:Combinatorial Chemistry Techniques; D003500:Cyclization; D007555:Isoxazoles / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D009589:Nitrogen Oxides / Q000138:chemical synthesis*; D013237:Stereoisomerism; D047090:beta-Lactams / Q000737:chemistry*
chemical_list: D001384:Azetidines; D007555:Isoxazoles; D009589:Nitrogen Oxides; D047090:beta-Lactams; C015388:nitrones