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The Role of Proximal, Lewis Basic Functional Groups in Carbonyl Reduction

3 The Role of Proximal, Lewis Basic Functional Groups in Carbonyl Reduction [Pg.30]

If chelation to a neigbouring group is possible, the use of HMPA is often not required for reduction of the carbonyl and reactions can be carried out under mild conditions. To examine the impact of chelation, Flowers studied the rate of reduction of 2-butanone, methyl acetoacetate and /V,/V-dimethylacetoace-tamide by Sml2.20 Reduction of the (1-keto ester or amide was several orders of magnitude faster than that of the unsubstituted ketone, which is consistent with chelation playing a major role. Further rate and mechanistic studies on the reduction of acetophenone and a series of 2 - and 4 -substituted acetophenone derivatives showed that both chelation and coordination provide highly [Pg.30]

In addition to accelerating the rate of carbonyl reduction, chelation can be used to control the diastereoselectivity of reductions and carbon-carbon bondforming reactions through highly organised transition states. Keck showed that appropriately subsituted p-hydroxy ketones are stereoselectively reduced by [Pg.31]

Even though the model shown above is consistent with the stereochemical outcome, Flowers has shown that changing the reaction conditions or the substituents in the (3-hydroxy ketone substrates can have an impact on the stereochemical outcome of the chelation-controlled reaction.23,24 A more detailed discussion of the mechanism of this reduction can be found in Chapter 4, Section 4.3. [Pg.32]

Although the above examples show the role played by substituents (3 to the ketone carbonyl, it is important to recognise that more distant, Lewis basic [Pg.32]




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Basic groups

Basicities reduction

Basicity Lewis

Basicity function

Carbonyl basicity

Carbonyl group basicity

Carbonyl group reduction

Carbonyl groups/functionalities

Carbonyl reduction

Carbonyl reduction Lewis basic functional groups

Functional carbonyl function

Functional group carbonyl groups

Functional group carbonyls

Functional reduction

Functionality basic

Group reduction function

In carbonyl groups

Lewis basic groups

Lewis basicity carbonyl

Of carbonyl group

Proximal

Proximates

Proximation

Proximity

Proximity function

Reduction carbonylation

Reduction function

Reduction functional groups

Reduction group

Reduction in carbonylation

Reduction of Functional Groups

Reduction of carbonyl groups

Reduction of carbonyls

Reduction of the carbonyl group

Reductive group

Role-functionalism

The Basics

The Carbonyl

The Carbonyl Group

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