Stereoselective Entry to Bicyclic β-Lactams via Free Radical Cyclization of 2-Azetidinone-Tethered Bromohomoallylic Alcohols

Triphenyltin hydride-promoted reaction of β-lactam-tethered bromodienes gave six-, seven-, or eight-membered bicyclic ring structures through intramolecular free radical cyclization. The cyclization precursors were synthesized by stereoselective tin-mediated carbonyl bromoallylation of 4-oxoazetidine-2-carbaldehydes in an aqueous environment.