Heterogeneous Catalysis in the Meerwein-Ponndorf-Verley Reduction of Carbonyl Compounds

Abstract

The Meerwein-Ponndorf-Verley (MPV) reaction involves the catalysed transfer of hydrogen from an alcohol to a carbonyl compound and provides an effective method for synthesizing carbonyl compounds under very mild conditions. The method, which requires the use of a catalyst, is high selective as it leaves most reducible functional groups in the carbonyl reactant untouched. The classical MPV reaction is conducted in a homogeneous phase, usually in the presence of a metal alkoxide as catalyst. The process has been extensively studied over the past 15 years, using heterogeneous catalysts that minimize or avoid many of the problems inherent in homogeneous catalysis. The most widely used among such catalysts consist of metal oxides (particularly aluminium, magnesium and zirconium oxides), magnesium phosphates, layered double hydroxides, mesoporous solids and zeolitic compounds. These materials vary widely in nature and include acid, basic, neutral, mesoporous and microporous solids. This allows virtually any type of carbonyl compound to be reduced by using an appropriate available catalyst. This paper reviews the most salient advances in MPV reduction processes involving heterogeneous catalysts, with emphasis of the reaction proper rather than on the nature of the catalyst. Special attention is given to the shape selectivity provided by zeolitic materials and layered double hydroxides for some carbonyl compounds.

Reactivity of Alcohols in Chemoselective Transfer Hydrogenation of Acrolein over Magnesium Oxide as the Catalyst

“…In general it has been stated that the reactivity of acrolein as the hydrogen acceptor from alcohols in the presence of MgO is very low compared to the reactivities determined for saturated carbonyl compounds [17,18,23,[27][28][29]. At 473 K the conversion of acrolein (results not shown) did not exceed 10%, whereas for saturated carbonyl compounds the conversions higher than 60% have been reported [17,18,23,27,29].…”

“…Metal oxides, MgO [11,12], ZrO 2 [13], double layered hydroxides [14], MgO-B 2 O 3 [15], and Al 2 O 3 -AlPO 4 [16] have been used as catalysts. According to literature data, MgO is one of the most active catalysts in CTH [17,18].…”

Catalytic hydrogen transfer over magnesia. Part XXV. Liquid and vapor phase reduction of ketoesters

“…For the first two members of this set of ketoesters, namely ethyl pyruvate (1) and ethyl acetoacetate (2), a fast uptake of these esters with time was observed. Although for pyruvate (1) and acetoacetate (2), conversions as high as 89 and 97 % after 1 h of reaction were noted, no products were found in liquid mixtures collected during tests. It was shown that the direct reaction between the above-mentioned esters and MgO occurs with the formation of a salt-like product, which is responsible for their uptake.…”

“…Catalytic hydrogen transfer, also known as catalytic transfer hydrogenation (CTH), is a useful method for the reduction of many aldehydes and ketones to the corresponding alcohols under mild conditions [1,2]. This reduction can be performed either in vapor or liquid phase, depending on the acceptor reactivity, with alcohols as hydrogen donors.…”

“…Recently, the catalysts obtained from hydrotalcites have also been used in CTH [12,[19][20][21]. According to the published works, MgO is one of the most efficient oxide catalysts in the CTH of carbonyl compounds with alcohols [1,2].…”