title: Synthesis of highly substituted 3-formylfurans by a gold(I)-catalyzed oxidation/1,2-alkynyl migration/cyclization cascade.
abstract: 3-Formylfuran derivatives are core structures of a variety of bioactive natural products. However, procedures for their preparation are still rare and generally inefficient in terms of atom economy: These methods require multiple steps or harsh reaction conditions and show selectivity problems. An efficient gold(I)-catalyzed cascade reaction that leads to 3-formylfurans from easily accessible starting materials is now described. A wide variety of 3-formylfurans were obtained from the corresponding symmetric and unsymmetric 1,4-diyn-3-ols in the presence of an N-oxide in good to excellent yields. Isotope-labeling experiments as well as DFT calculations support a mechanism in which, after an initial oxygen transfer, a 1,2-alkynyl migration is favored over a hydride shift; a cyclization ensues to afford the desired functionalized furan core.
authors.affiliation: Organisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg (Germany) http://www.hashmi.de.
authors.forename: Tao
authors.initials: T
authors.lastname: Wang
authors.forename: Shuai
authors.initials: S
authors.lastname: Shi
authors.forename: Max M
authors.initials: MM
authors.lastname: Hansmann
authors.forename: Eva
authors.initials: E
authors.lastname: Rettenmeier
authors.forename: Matthias
authors.initials: M
authors.lastname: Rudolph
authors.forename: A Stephen K
authors.initials: AS
authors.lastname: Hashmi
mesh_terms: D000480:Alkynes / Q000737:chemistry*; D002384:Catalysis; D003500:Cyclization; D005663:Furans / Q000138:chemical synthesis* / Q000737:chemistry; D006046:Gold / Q000737:chemistry*; D015394:Molecular Structure; D010084:Oxidation-Reduction; D013237:Stereoisomerism
chemical_list: D000480:Alkynes; D005663:Furans; D006046:Gold; C039281:furan
keywords: N-oxides; alkynyl migration; cyclization; furans; gold