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.
In the presence of a phenol ligand, a cationic ruthenium hydride complex exhibited high catalytic activity for the hydrogenolysis of carbonyl compounds to yield the corresponding aliphatic products. The reaction showed exceptionally high chemoselectivity toward the carbonyl reduction over alkene hydrogenation.
N. Kalutharage, C. S. Yi, J. Am. Chem. Soc., 2015, 137, 11105-11114.
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.
Two complementary dual catalytic systems enable a highly regioselective reductive hydration of terminal alkynes to yield branched or linear alcohols in very good yield. The method is compatible with terminal, di-, and trisubstituted alkenes. This reductive hydration constitutes a strategic surrogate to alkene oxyfunctionalization and may be of utility in multistep settings.
L. Li, S. B. Herzon, J. Am. Chem. Soc., 2012, 134, 17376-17378.
In a highly regio- and stereoselective hydroarylation, hydroalkenylation, and hydrobenzylation of ynol ethers, a Pd-catalyzed reductive addition of organohalides, including aryl, alkenyl, and benzyl halides, in the presence of 2-propanol gives α,β- and β,β-disubstituted olefinic ethers in good yields.
W. Cui, J. Yin, R. Zheng, C. Cheng, Y. Bai, G. Zhu, J. Org. Chem., 2014, 79, 3487-3493.
Aryl halides are reduced into the corresponding arenes in high yields, using 2-propanol as reductant and solvent, cesium carbonate as base, and di-tert-butyl peroxide (or di-tert-butyl hyponitrite) as radical initiator. This simple system reduces various aryl bromides and iodides through a SET mechanism with high functional-group tolerance.
R. Ueno, T. Shimizu, E. Shirakawa, Synlett, 2016, 27, 747-744.
A simple and efficient Ru(II)-catalyzed transfer hydro-dehalogenation using 2-propanol as the hydride source is applicable for various aromatic halides and α-haloesters and amides. The potential synthetic application of this method was demonstrated by efficient gram-scale transformation with catalyst loading as low as 0.5 mol %.
T. You, Z. Wang, J. Chen, Y. Xia, J. Org. Chem., 2017, 82, 1340-1346.