Unique synthetic utility of BF3 center dot OEt2 in the highly diastereoselective reduction of hydroxy carbonyl and dicarbonyl substrates

GRAPHICS A new aspect of commonly used BF3. OEt2 has been illuminated by successfull y demonstrating the unique but highly stereoselective reactions of hydroxy carbonyl and dicarbonyl substrates, For example, treatment of gamma-hydroxy ketone 1c with BF3 . OEt2/Bu3SnH in CH2Cl2 at -78 to -40 degrees C afforde d the corresponding 1,4-diol 2c with virtually complete diastereoselection, while use of TiCl4 as a Lewis acid under similar reaction conditions cause d a total lack of diol yield and selectivity (17%; 2c/3c = 1.2:1), accompan ied by a significant formation of 2,3-disubstituted tetrahydrofuran 4 (44%) .