Efficient entry to highly functionalized β-lactams by regio- and stereoselective 1,3-dipolar cycloaddition reaction of 2-azetidinone-tethered nitrones. Synthetic applications

Article abstract of DOI:10.1021/jo025924e

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-β-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 β-lactams or functionalized β-alkoxycarbonyl γ-lactams (derivatives of the aza analogue of paraconic acid).