title: Acetal-vinyl sulfide cyclization on sugar substrates: effect of structure and substituent.
abstract: A range of 2-deoxyfuranoside and -pyranoside derivatives were fashioned into derivatives that carry a vinyl or propenyl side chain. Extension of the alkene by a Suzuki cross-coupling reaction with 1-bromo-1-(phenylthio)ethene gave thioenol ethers as the cyclization substrates. The treatment of these substrates with BF(3).Et(2)O in tert-butylmethyl ether below 0 degrees C induced cyclization to optically active bicyclic ethers. If the cyclizations are carried out in toluene as the solvent, the isomerization of the terminal thioenol ether to the inner thioenol ether can take place prior to the cyclization. The cyclization reactions can be impeded by steric and electronic factors. The opening of the bicyclic ethers could be illustrated with the base-induced conversion of the ketone 53 to the cyclooctenone 54.
authors.affiliation: Institut für Organische Chemie, Universität Tübingen, Auf der Morgenstelle 18, D-72076 Tübingen, Germany.
authors.forename: Pradip K
authors.initials: PK
authors.lastname: Sasmal
authors.forename: Martin E
authors.initials: ME
authors.lastname: Maier
mesh_terms: D002384:Catalysis; D003500:Cyclization; D004987:Ethers / Q000737:chemistry; D005663:Furans / Q000737:chemistry; D005960:Glucosides / Q000138:chemical synthesis* / Q000737:chemistry*; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D011714:Pyrans / Q000737:chemistry; D013237:Stereoisomerism; D014752:Vinyl Chloride / Q000737:chemistry
chemical_list: D004987:Ethers; D005663:Furans; D005960:Glucosides; D011714:Pyrans; D014752:Vinyl Chloride