Reductive coupling between aromatic aldehydes and ketones or imines by copper catalysis
The copper-catalyzed reductive coupling of two different carbonyl compounds has been achieved. The reaction of aromatic aldehydes and arylketones with a silylboronate in the presence of a catalytic amount of a CuCl-N-heterocyclic carbene (NHC) complex and a stoichiometric amount of alkoxide base yielded cross-coupled 1,2-diol derivatives. A reaction pathway is proposed that involves the catalytic formation of a nucleophilic α-silyloxybenzylcopper(I) species from the aromatic aldehyde and its subsequent coupling with the arylketone. This process was amenable to asymmetric catalysis. This copper catalyst system also enabled the reductive coupling between aromatic aldehydes and imines.
Samarium Dibromide, an Efficient Reagent for the Pinacol Coupling Reactions.
The preparation of SmBr2 from Sm2O3 is described.This samarium (II) compound is a powerful one electron reductant able to very efficiently mediate pinacolic couplings.Cross couplings are effective in some cases, for example a chiral diol can be obtained from benzophenone and camphor.Intramolecular pinacolization of a diketone has been performed.
Lebrun, Alain,Namy, Jean-Louis,Kagan, Henri B.
p. 2311 - 2314
(2007/10/02)
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