Selectivity in the Free-Radical Reduction of Lactones with Trichlorosilane
Each of the generally recognized methods for converting lactones to cyclic ethers suffers from distinct structural limitations. For instance, Adams catalyst in an acidic medium will reduce δ-lactones to the corresponding ethers but fails completely with γ- and ε-lactones.2 Pettit's reagents derived from complex metal hydrides and boron trifluoride are very effective when the alcohol portion of the lactone is tertiary, but the yields of ethers decrease dramatically as substitution at the alcohol portion is decreased.3 Published results suggest a further limitation to the Pettit procedure when the lactone is part of an otherwise flexible system that can adopt a more favorable conformation by ring opening. For instance, Bruice4 has reported that no ether is formed on reduction of 2-oxabicyclo[ 2.2.2]octan-3-one (1) with BF3-B2H6 and we have encountered a similar failure with 6-oxabicyclo[3.2.1 Joctan-7-one (2). © 1974, American Chemical Society. All rights reserved.
Baldwin, SW; Doll, RJ; Haut, SA
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