ChemInform Abstract: Free-Radical Reduction Reactions of Chiral Dihydronicotinamides. Enantioselective Hydrogen Atom Transfer and Electron-Transfer Processes During the Reduction of Ketones.
Abstract
If the reduction of (I) with DHNA to alcohol (II) (yield 43%) is carried out in the presence of m-dinitrobenzene (inhibitor), the yield is diminished (13%), whereas with additive AIBN (initiator) the yield is dramatically enhanced (see scheme); however, the e.e.'s are not at all influenced by either additive.
ChemInform Abstract
If the reduction of (I) with DHNA to alcohol (II) (yield 43%) is carried out in the presence of m-dinitrobenzene (inhibitor), the yield is diminished (13%), whereas with additive AIBN (initiator) the yield is dramatically enhanced (see scheme); however, the e.e.'s are not at all influenced by either additive. These results constitute the first experimental evidence for a free-radical chain reaction whose propagation step contains an enantioselective H atom transfer, while the reduction of (±)-fenchone (IV) constitutes the first example of an enantioselective electron-transfer reaction.
