Metal-Catalyzed Cycloisomerization and Tandem Oxycyclization/Hydroxylation of Alkynols: Synthesis of Nonfused, Spiranic and Fused Oxabicyclic β-Lactams

8 páginas, 11 esquemas. El documento en word es el artículo post-print.2-Azetidinone-tethered alkynols, readily prepared from the corresponding aldehydes or ketones, were used as starting materials for the oxycyclization reaction catalyzed by precious metals. AgOAc exclusively affords dihydrofurans, methylenetetrahydrofurans, or methylenetetrahydro-2H-pyrans through specific 5-endo, 5-exo, or 6-exo pathways, respectively. Interestingly, in the presence of a catalytic amount of PtII or AuIII salts, cyclization reactions occurred preferentially through a tandem oxycyclization/hydroxylation of alkynols to afford a variety of nonfused, spiranic and fused oxabicyclic β-lactams in moderate to high yields. Besides, it has been observed that the tandem gold-catalyzed cycloetherification/hydroxylation of a methoxymethyl alkynyl ether can be accomplished.We would like to thank the Dirección General de Investigación- Ministerio de Ciencia e Innovación (DGI-MICINN) (Project CTQ2009-09318), Universidad Complutense-Banco Santander Central Hispano (UCM-BSCH) (Grant GR58/08), and Comunidad Autónoma de Madrid (CAM) (Project S2009/PPQ-1752) for financial support. T.M.C. and R.C. thank theMICINN for predoctoral grants.Peer reviewe