title: Domino reactions of 1,3-bis-silyl enol ethers with benzopyrylium triflates: efficient synthesis of fluorescent 6H-benzo[c]chromen-6-ones, dibenzo[c,d]chromen-6-ones, and 2,3-dihydro-1H-4,6-dioxachrysen-5-ones.
abstract: The condensation of 1,3-bis-silyl enol ethers with benzopyrylium triflates, generated in situ by the reaction of chromones with Me3SiOTf, afforded functionalized 2,3-dihydrobenzopyrans; treatment of the latter with NEt3 or BBr3 resulted in a domino retro-Michael-aldol-lactonization reaction and the formation of a variety of 7-hydroxy-6H-benzo[c]chromen-6-ones. The hydroxy group was functionalized by using Suzuki cross-coupling reactions. The methodology reported was applied to the synthesis of the natural product autumnariol and a new fluorescence dye, which exhibits promising optical properties. 2,3-Dihydro-1H-4,6-dioxachrysen-5-ones were prepared by condensation of chromones with 1,3-bis-silyl enol ethers containing a remote chloride group, domino retro-Michael-aldol-lactonization, and an intramolecular Williamson reaction.
authors.affiliation: Institut für Chemie und Biochemie, Universität Greifswald, Soldmannstrasse 16, 17487 Greifswald, Germany.
authors.forename: Bettina
authors.initials: B
authors.lastname: Appel
authors.forename: Nehad N R
authors.initials: NN
authors.lastname: Saleh
authors.forename: Peter
authors.initials: P
authors.lastname: Langer
mesh_terms: D002867:Chromones / Q000138:chemical synthesis* / Q000737:chemistry; D004987:Ethers / Q000737:chemistry*; D008698:Mesylates / Q000737:chemistry*
chemical_list: D002867:Chromones; D004987:Ethers; D008698:Mesylates