Reductive Coupling of Benzoyl Cyanide and Carbonyl Compounds by Aqueous Ti(III) Ions. A New Convenient and Selective Access to the Less Stable Mixed Benzoins
The reactive species formed by the Ti(III) ion reduction of benzoyl cyanide (1) adds to the C-atom of carbonyl compounds 2 under simple experimental conditions.The intermediate 1,2-diols 3 are smoothly converted, without isolation, into the less thermodynamically stable mixed benzoins 4, which are not accessible by the classical benzoin condensation.The possible mechanisms involved in the reaction are discussed.
Clerici, Angelo,Porta, Ombretta
p. 2889 - 2893
(2007/10/02)
Reduction of Unsymmetrical Benzils Using Sodium Dithionite
Contrary to a previous report, reduction of unsymmetrical benzils by sodium dithionite (sodium hydrosulfite) in general yields a mixture of isomeric benzoins.Whereas the reduction of aldehydes and ketones by dithionite apparently takes place by a nucleophilic addition mechanism, the reduction of benzils proceeds by an electron-transfer mechanism.The initial product of the reduction is the (Z)-α,α'-stilbenediol which is produced stereospecifically.The ultimate benzoin products, then, result from the two different modes of ketolization of the stilbenediol intermediate.
Heilmann, Steven M.,Rasmussen, Jerald K.,Smith, Howell K.
p. 987 - 992
(2007/10/02)
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