title: A mild, diastereoselective construction of cyclic and spirocyclic ketals employing a tandem photoisomerization/cyclization tactic.
abstract: The cyclization of trans-δ-hydroxy enones to cyclic mixed ketals routinely requires superstoichiometric strong acid. By operating under a photoisomerization regime, the cyclization of trans-δ-hydroxy enones proceeds under catalytic Brønsted acid to provide cyclic ketals or unsaturated spiroketals in a highly diastereoselective fashion. A one-pot, two-step protocol was thus developed to provide cyclic methoxy ketals with a free β-hydroxy group for future functionalization.
authors.affiliation: Department of Chemistry, Laboratory for Research on the Structure of Matter and Monell Chemical Senses Center, University of Pennsylvania , Philadelphia, Pennsylvania 19104, United States.
authors.forename: Bo
authors.initials: B
authors.lastname: Li
authors.forename: Brett D
authors.initials: BD
authors.lastname: Williams
authors.forename: Amos B
authors.initials: AB
authors.lastname: Smith
mesh_terms: D002384:Catalysis; D003500:Cyclization; D005663:Furans / Q000138:chemical synthesis* / Q000737:chemistry; D007659:Ketones / Q000737:chemistry*; D015394:Molecular Structure; D013141:Spiro Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism
chemical_list: D005663:Furans; D007659:Ketones; D013141:Spiro Compounds; C520774:spiroketal