Meerwein–Ponndorf–Verley reduction

[1] The advantages of the MPV reduction lie in its high chemoselectivity and its use of a cheap environmentally friendly metal catalyst.

MPV reductions have been described as "obsolete" owing to the development of sodium borohydride and related reagents.

[2] The MPV reduction was independently discovered by Albert Verley and the team of Hans Meerwein and Rudolf Schmidt in 1925.

[5] The MPV reduction is believed to go through a catalytic cycle involving a six-member ring transition state as shown in Figure 2.

Groups, such as alkenes and alkynes, that normally pose a problem for reduction by other means have no reactivity under these conditions.

[7] The aluminium based Meerwein–Ponndorf–Verley reduction can be performed on prochiral ketones leading to chiral alcohols.

One method of achieving the asymmetric MPV reduction is with the use of chiral hydride donating alcohols.

[8] This enantioselection is due to the sterics of the two phenol groups in the six membered transition state as shown in Figure 3.

[9] By tethering the ketone to the hydride source only one transition state is possible (Figure 4) leading to the asymmetric reduction.

Chiral ligands on the aluminium alkoxide can affect the stereochemical outcome of the MPV reduction.

[7] Finally, in some cases the alcohol generated by the reduction can be dehydrated giving an alkyl carbon.