Borane- and Silylium-Catalyzed Difunctionalization of Carbohydrates: 3,6-Anhydrosugar Enabled 1,6-Site Selectivity
Joshua J Clarke1, Kevin Basemann1, Neyen Romano1
1Caudill Laboratories, Department of Chemistry, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States.
Abstract:
A novel diastereoselective, Lewis acid catalyzed 1,6-difunctionalization of galactose and mannose derivatives has been developed in one pot, via sequential nucleophile additions. Our studies point to the formation of a 3,6-anhydrosugar intermediate as key to the 1,6-site-selectivity. Starting material-specific reactivity occurs when competitive ring-opening C-O cleavage is possible, owed to basicity and stereoelectronic stabilization differences. Lastly, Mayr nucleophilicity parameter values helped predict which reaction conditions would be most suitable for specific nucleophiles.
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