Reactions of 2-Hydroxy-6,8-dioxabicyclo[3.2.1]oct-3-ene with Diethylaminosulfur Trifluoride and with Halogens. Facile Synthesis of 1,6-Anhydrohalohexopyranoses

Franz Oberdorfer; Roland Haeckel; Gilbert Lauer

doi:10.1055/s-1998-4484

Synthesis 1998; 1998(2): 201-206
DOI: 10.1055/s-1998-4484

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Reactions of 2-Hydroxy-6,8-dioxabicyclo[3.2.1]oct-3-ene with Diethylaminosulfur Trifluoride and with Halogens. Facile Synthesis of 1,6-Anhydrohalohexopyranoses

Franz Oberdorfer^* , Roland Haeckel, Gilbert Lauer

^*Deutsches Krebsforschungszentrum, Abteilung Radiochemie, Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany; Fax + 49(62 21)42 25 72; E-mail: oberdorfer@dkfz-heidelberg.de

Abstract

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d-Galactal 1 reacts in THF in the presence of catalytic amounts of concentrated sulfuric acid to give (2R)-2-hydroxy-6,8-dioxabicyclo[3.2.1]oct-3-ene (4) in a Ferrier-type rearrangement in 40% yield. When 4 is treated with diethylaminosulfur trifluoride (DAST) under certain reaction conditions, a novel intramolecular second order allylic rearrangement follows leading to previously unknown diastereomeric monofluoro derivatives 7 and 8. Direct α-substitution of 4 by DAST affords the 2-monofluoro derivative 6 under kinetic control. When DAST is used with dimethylformamide as solvent an apparent [1,3] sigmatropic migration of the 2-hydroxy group of 4 gives (4S)-4-hydroxy-6,8-dioxabicyclo[3.2.1]oct-2-ene (9). The corresponding 4-fluoro-substituted product was not obtained from the reaction of 9 with DAST. Oxidation of 4 and repeated treatment with DAST gives a novel 2,2-difluoro compound 11. Electrophilic addition of bromine to protected 4 afforded the 1,6-anhydromonobromo- and -dibromohexopyranoses 15-17. Monohalo and monopseudohalo derivatives (-F, -Cl, -Br, -N₃) 22-25 were prepared by nucleophilic oxirane ring opening of the easily available endo-epoxides 18-20.

diethylaminosulfur trifluoride - glycal rearrangement - dioxabicyclooctenes - 1,6-anhydrohalohexopyranoses - hexose epoxides

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