title: Mechanistic insights into the vanadium-catalyzed Achmatowicz rearrangement of furfurol.
abstract: The Achmatowicz rearrangement is a powerful method for the construction of pyranones from simple furan derivatives. Here, we describe the development of improved reaction conditions and an interrogation into the fate of the metal center during this interesting transformation. The reaction to form the synthetically important lactol, 6-hydroxy-2H-pyran-3(6H)-one (3), proceeds cleanly in the presence of tert-butyl hydroperoxide (TBHP, 2) using low loadings of VO(O(i)Pr)3 as catalyst. The nonaqueous conditions developed herein allow for easy isolation of product 3 and synthetically important derivatives, a key advantage of this new protocol. Detailed experimental, spectroscopic, and kinetic studies along with kinetic modeling of the catalytic cycle support a positive-order dependence in both furfurol and TBHP concentrations, first-order dependence in catalyst (VO(O(i)Pr)3), and a negative dependence on the 2-methyl-2-propanol (4) concentration. (51)V-NMR spectroscopic studies revealed that 2-methyl-2-propanol (4) competes with substrates for binding to the metal center, rationalizing its inhibitory effect.
authors.affiliation: Department of Chemistry, The Scripps Research Institute , 10550 North Torrey Pines Road, La Jolla, California 92037, United Sates.
authors.forename: Yining
authors.initials: Y
authors.lastname: Ji
authors.forename: Tamas
authors.initials: T
authors.lastname: Benkovics
authors.forename: Gregory L
authors.initials: GL
authors.lastname: Beutner
authors.forename: Chris
authors.initials: C
authors.lastname: Sfouggatakis
authors.forename: Martin D
authors.initials: MD
authors.lastname: Eastgate
authors.forename: Donna G
authors.initials: DG
authors.lastname: Blackmond
mesh_terms: D002384:Catalysis; D018360:Crystallography, X-Ray; D005663:Furans / Q000737:chemistry*; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D014639:Vanadium / Q000737:chemistry*; D020122:tert-Butylhydroperoxide / Q000737:chemistry*
chemical_list: D005663:Furans; D009942:Organometallic Compounds; D014639:Vanadium; D020122:tert-Butylhydroperoxide