Novel, simple, and convenient strategies to diversely functionalized spirocyclic β-lactams have been developed by using different metal-mediated carbonyl addition/cyclization reaction sequences. Spirocyclization precursors, 2-azetidinone-tethered homoallylic alcohols, bromohomoallylic alcohols, homopropargylic alcohols, (buta-1,3-dien-2-yl)methanols, and α-allenols have been obtained by regioselective addition of stabilized organometallic reagents to azetidine-2,3-diones in an aqueous environment. Ruthenium-, silver-, and palladium-catalyzed reactions of the above monocyclic unsaturated alcohol derivatives provided oxaspiro-β-lactams.