A convenient disproportionation or reduction of aldehydes is promoted by lithium bromide and triethylamine in a solvent-free environment at room temperature. Products of Cannizzaro or Tishchenko reactions can be isolated using different workup methods. In the presence of a hydrogen donor alcohol, a Meerwein-Ponndorf-Verley reaction takes place.
M. M. Mojtahedi, E. Akbarzadeh, R. Sharifi, M. S. Abaee, Org. Lett., 2007, 9, 2791-2793.
The reduction of ketones and aldehydes with lanthanide metals (La, Ce, Sm, Yb) and a catalytic amount of iodine (5 mol %) in iPrOH proceeded smoothly to produce the corresponding alcohols as the major products in good yield, while in THF, methanol, and ethanol the pinacols were mainly produced. The yields of alcohols were improved most effectively by the use of Sm metal.
S.-I. Fukuzawa, N. Nakano, T. Saitoh, Eur. J. Org. Chem., 2004, 2863-2867.
Pincer-aryl ruthenium(II) complexes form active catalysts in the reduction of ketones by hydrogen transfer in iPrOH using KOH as promoter. At a KOH/Ru molar ratio of 20/1 only trace amounts of aldol products are formed. Under these conditions, the σ Ru-C bond is stable and the [Ru(PCP)PPh3] fragment is preserved.
P. Dani, T. Karlen, R. A. Gossage, S. Gladiali, G. van Koten, Angew. Chem., 2000, 112, 759-761.
An asymmetric α-alkylative reduction of prochiral ketones with primary alcohols has been disclosed. The reaction is catalyzed by both iridium and ruthenium complexes and gave optically active alcohols with elongation of the carbon skeleton with high enantioselectivity.
G. Onodera, Y. Nishibayashi, S. Uemura, Angew. Chem. Int. Ed., 2006, 45, 3819-3822.
Enantioselective transfer hydrogenation of 1,1-dimethylallene in the presence of aldehydes and 2-propanol or primary alcohols without 2-propanol employing a cyclometalated iridium C,O-benzoate derived from allyl acetate, m-nitrobenzoic acid, and (S)-SEGPHOS delivers reverse-prenylation products in very good yields and enantioselectivities.
S. B. Han, I. S. Kim, H. Han, M. J. Krische, J. Am. Chem. Soc., 2009, 131, 6916-6917.