Meerwein -Ponndorf- Verley reduction

The Meerwein-Ponndorf-Verley procedure has largely been replaced by reduction procedures that use lithium aluminum hydride, sodium borohydride or derivatives thereof. The Meerwein-Ponndorf-Verley reduction however has the advantage to be a mild and selective method, that does not affect carbon-carbon double or triple bonds present in the substrate molecule. 

The lithium aluminum hydride-aluminum chloride reduction of ketones is closely related mechanistically to the Meerwein-Ponndorf-Verley reduction in that the initially formed alkoxide complex is allowed to equilibrate between isomers in the... 

Secondary alcohols may be oxidised to the corresponding ketones with aluminium /erl.-butoxide (or tsopropoxide) in the presence of a large excess of acetone. This reaction is known as the Oppenauer oxidation and is the reverse of the Meerwein - Ponndorf - Verley reduction (previous Section) it may be expressed ... 

We recently reported a modified Meerwein-Ponndorf-Verley reduction in which low-boiling alcohols such as EtOH and w-PrOH, but preferably i-PrOH, were used at temperatures near 225 °C in the absence of aluminum alkoxides [42]. The carbonyl moiety of an olefinic aldehyde such as cinnamaldehyde was reduced selectively to the alcohol without the carbon-carbon double bond being affected (Scheme 2.7). Since base was not present, aldol and Claisen-Schmidt condensations were avoided. 

Transfer Hydrogenation Including the Meerwein-Ponndorf-Verley Reduction... 

Meerwein-Ponndorf-Verley Reduction and Oppenauer Oxidation... 

The most common catalysts for the Meerwein-Ponndorf-Verley reduction and Oppenauer oxidation are Alm and Lnm isopropoxides, often in combination with 2-propanol as hydride donor and solvent. These alkoxide ligands are readily exchanged under formation of 2-propanol and the metal complexes of the substrate (Scheme 20.5). Therefore, the catalytic species is in fact a mixture of metal alkoxides. 

As shown in Figure 1.26, a chiral Sm(III) complex catalyzes asymmetric reduction of aromatic ketones in 2-propanol with high enantioselectivity. Unlike other late-transition-metal catalysis, the hydrogen at C2 of 2-propanol directly migrates onto the carbonyl carbon of substrate via a six-membered transition state 26A, as seen in the Meerwein-Ponndorf-Verley reduction. ... 

The Meerwein-Ponndorf-Verley reduction (reduction with aluminum alkoxides). Wilds, A.L., Org. Reactions 2, 178 (1944). 

Mannich reaction, 1, 10 7, 3 Meerwein arylation reaction, 11, 3 24, 3 Meerwein-Ponndorf-Verley reduction, 2, 5 Mercury hydride method to prepare radicals, 48, 2... 

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