3-Spirocyclopropane P-lactam

Analogously, in 2004, it has been reported that the treatment of bis-spirocy-clopropanated isoxazolidines [202-207] with TFA in acetonitrile furnished the 3-spirocyclopropanated p-lactams in 75-96% yields [208]. 

Scheme 43 Three component cascade reaction to afford 3 spirocyclopropanated P lactams...

Spiro- and 4,5-bis(spiro)-cyclopropane isoxazolidines 85a and 85b prepared by 1,3-DC of acyclic nitrones with methylenecyclopropane (MCP), MCP derivatives or bicyclopropylidene (BCP) smoothly underwent fragmentation upon heating in the presence of a protic acid to yield monobactams 86a and spirocyclopropanated p-lactams 86b in moderate to good yields (56-96%) <04EJ02205 04EJO4158>. 

Spirocyclopropane isoxazolidines 75, obtained from alkylidenecyclopropane nitrones, underwent thermally induced selective rearrangement to pyrrolo[3,4-A]pyridinones 76 <00TA897>. The same adducts 75 in the presence of a protic acid afforded exclusively p-lactams 77 (57-60% yield) accompanied by ethylene extrusion <00JA8075>. 

Thermolysis of 3,4-cw ring-fused 5-spirocyclopropane isoxazolidines in the presence of a protic acid, yielded 3,4-cw ring-fused azetidin-2-ones 51 with concomitant extrusion of ethylene <03JOC3271>. Bicyclic isoxazolidines have been converted into the corresponding P-lactams by sequential N-O bond cleavage, oxidation and cyclization <03JOC1207>. Intramolecular aromatic nucleophilic substitution has been established as a route for tricyclic P-lactams 52 <03T5259>. 

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