title: Discovery and Development of a Three-Component Oxidopyrylium [5 + 2] Cycloaddition.
abstract: α-Hydroxy-γ-pyrone-based oxidopyrylium cycloaddition reactions are useful methods for accessing a highly diverse range of oxabicyclo[3.2.1]octane products. Intermolecular variants of the reaction require the formation of a methyl triflate-based pre-ylide salt that upon treatment with base in the presence of alkenes or alkynes leads to α-methoxyenone-containing bicyclic products. Herein, we describe our discovery that the use of ethanol-stabilized chloroform as solvent leads to the generation of α-ethoxyenone-containing bicyclic byproducts. This three-component process was further optimized by gently heating a mixture of a purified version of the oxidopyrylium dimer in the presence of an alcohol prior to addition of a dipolarophile. Using this convenient procedure, several new oxidopyrylium cycloaddition products can be generated in moderate yields. We also highlight the method in a tandem ring-opening/debenzylation method for the generation of α-hydroxytropolones.
authors.affiliation: Department of Chemistry, Brooklyn College, The City University of New York , Brooklyn, New York 11210, United States.|PhD Program in Chemistry, The Graduate Center of The City University of New York , New York, New York 10016, United States.
authors.forename: Michael P
authors.initials: MP
authors.lastname: D'Erasmo
authors.affiliation: Department of Chemistry, Brooklyn College, The City University of New York , Brooklyn, New York 11210, United States.|PhD Program in Chemistry, The Graduate Center of The City University of New York , New York, New York 10016, United States.
authors.forename: Christine
authors.initials: C
authors.lastname: Meck
authors.affiliation: Department of Chemistry, Cornell University , Ithaca, New York 14853, United States.
authors.forename: Chad A
authors.initials: CA
authors.lastname: Lewis
authors.affiliation: Department of Chemistry, Brooklyn College, The City University of New York , Brooklyn, New York 11210, United States.|PhD Program in Chemistry, The Graduate Center of The City University of New York , New York, New York 10016, United States.
authors.forename: Ryan P
authors.initials: RP
authors.lastname: Murelli
mesh_terms: D001643:Bridged Bicyclo Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D061565:Cycloaddition Reaction; D034242:Cyclooctanes / Q000138:chemical synthesis / Q000737:chemistry*; D011753:Pyrones / Q000737:chemistry*; D013237:Stereoisomerism; D014334:Tropolone / Q000737:chemistry*
chemical_list: D001643:Bridged Bicyclo Compounds; D034242:Cyclooctanes; D011753:Pyrones; D014334:Tropolone