ABSTRACT
Highly-functionalised difluorinated cyclooctenones were synthesised from trifluoroethanol using either metallated difluoroenol acetal or carbamate chemistry, followed by a [2,3]-Wittig rearrangement or aldol reaction. Efficient RCM reactions afforded the title compounds which showed rather restricted fluxional behaviour by VT (19)F NMR. Topological characterisation by molecular modelling and NOESY/ROESY experiments offered a number of challenges, but allowed the identification of two favoured boat-chair conformers which interconverted by pseudorotation with relatively large activation barriers.
Subject(s)
Carbohydrates/chemistry , Fluorine/chemistry , Hydrocarbons, Aromatic/chemistry , Hydrocarbons, Aromatic/chemical synthesis , Molecular Mimicry , Magnetic Resonance Spectroscopy , Models, Molecular , Molecular Conformation , Spectrometry, Mass, Fast Atom BombardmentABSTRACT
Topologically mobile difluorinated cyclooctenones undergo rapid, high-yielding, and completely stereoselective epoxidations with methyl(trifluoromethyl)dioxirane. The epoxides resist conventional hydrolysis but react smoothly in basic media under microwave irradiation to afford unique hemiacetals and hemiaminals in good yield. [reaction: see text]
Subject(s)
Cyclohexanones/chemistry , Epoxy Compounds/chemistry , Ethylene Oxide/analogs & derivatives , Microwaves , Acetals/chemistry , Chemistry, Organic , Ethylene Oxide/chemistry , Fluorine/chemistry , Hydrolysis , Molecular Structure , Organic Chemistry Phenomena , Oxidation-Reduction , StereoisomerismABSTRACT
Difluorinated cyclooctenones, synthesised using RCM, can be used as templates for stereoselective oxidative transformations to products that undergo transannular reactions to afford conformationally-locked analogues of 2-deoxy-2,2-difluorosugars with different stereochemical relationships between the C-2 and C-3 hydroxyl groups.
