The presence of water improves reductive openings of benzylidene acetals with trimethylaminoborane and aluminium chloride

The acidic reagent formed in situ from anhydrous AlCl 3 and H 2O in 3:1 ratio is much more efficient for the reductive openings of the cyclic benzylidene acetals with Me 3N·BH 3 in tetrahydrofurane than the AlCl 3 alone. Under proposed conditions, the dioxane-type 4,6- O-bezylidene acetals of hexopy...

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Bibliographic Details
Published in:Carbohydrate research 2003-04, Vol.338 (8), p.697-703
Main Authors: Sherman, Andrei A., Mironov, Yuri V., Yudina, Olga N., Nifantiev, Nikolay E.
Format: Article
Language:English
Subjects:
Acetals - chemistry
Aluminum Compounds - chemistry
Benzylidene acetal
Benzylidene Compounds - chemistry
Boranes - chemistry
Chlorides - chemistry
Hexopyranosides
Hexoses - chemistry
Magnetic Resonance Spectroscopy
Oxidation-Reduction
Protecting group
Reductive opening
Stereoisomerism
Water
Water - chemistry
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Summary:The acidic reagent formed in situ from anhydrous AlCl 3 and H 2O in 3:1 ratio is much more efficient for the reductive openings of the cyclic benzylidene acetals with Me 3N·BH 3 in tetrahydrofurane than the AlCl 3 alone. Under proposed conditions, the dioxane-type 4,6- O-bezylidene acetals of hexopyranosides give regioselectively the corresponding 4-hydroxy,6- O-benzyl derivatives in excellent yields. Reductive openings of the dioxolane-type 3,4- O-benzylidene acetals of galactopyranoside are also very efficient and regioselective and give either 3- O-benzyl derivative (from 3,4- O- exo-benzylidene acetal) or 4- O-benzyl derivative (from 3,4- O- endo-benzylidene acetal) depending on the configuration of the acetal carbon atom. Graphic
ISSN:0008-6215
1873-426X
DOI:10.1016/S0008-6215(03)00015-6