T. Weiß31. Mai 2005Seite1

Solid phase organic reactions, part 2

(reduction, oxidation, formation of carbonyl compounds and derivatives thereof)

NMe3 ClCrO3

NMe3 BH4

NMe3 RuO4

NMe3 BH3CN

IOAc

OAc

SnBu

HBu

NN OsO4

Cl

O

NBH

O

PhPh

O

O

SO

O O5

O

PPH2

N Zn(BH4)2

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Polymer-supported reagents (PSR)

Advantages

Simplification of reaction work-up and product isolation

Reaction can be driven to completion

Potential of recycling

Higher stability, reduced toxicity

Two incompatible reagents can be used at the same time

Simplified automation

Disadvantages

Reduced activity due to unfavorable electronic and steric interaction

Slower reaction - long reaction times

Poor yields

Low loading of polymer

Large scale reactions not practicable

Leaching of metal

reagent A B reagent Bfiltrationreaction

condition

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X Y solid phasechemistry

reactive moiety X Y reactive moietycovalent bond

polymerizationreactive moiety reactive moiety

covalent bond

NMe3 ion exchangechemistry

NMe3

ionic interaction

X-reagent

reagent

Entrapment, reagent enclosed in a polystyrene network

Methods for preparing PSR

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Types of reactionA few reagents for oxidation

Oxidation of alcoholsPolymer-supported perruthenatePolymer-bound sulfoxide for swern reactionPolymer-supported chrom-basedand manganese-based oxidantsTEMPO-resin

Ozonolysisworking-up with polymerbound phosphanesor sulfides

HydroformylationPolymer-supported rhuthenium-complexes

N-oxidation, S-oxidationPolymer-bound oxirane

Formation of chinonesPolymer-supported hypervalent iodine

R1 R2

OH

R1 R2

O

R1

R2

R1

CHOR2

R2 R3

R1R1

O

R2 R3

Oi) O3

ii)

N NO

O

O

OH

OH

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EpoxidationPolymer-supported Mn-salene-complexes

Asymmetric Dihydroxylation (AD)Polymer-bound Sharpless-reagent

NtBu

O

NMn

OCl

N

R

R R

R

R R

O

N

N

NN

RO

ODHQD

ODHQD

R2 R3

R1HO

R3R2

OHR1 H

co-oxidant

R1

R2O

R1

R2

NMO, mCPBA

Types of reactionA few reagents for oxidation

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Types of reactionExamples for reduction

R1 R2

O

R1 R2

OH

R1

O

R2 R3

HN

R4R1 R2

NR3 R4

R1 NO2 R1 NH2

CuCl

R1 X R1 H

X= Br, Cl, OC(S)OPh

Reduction of carbonylsPolymer-supported borohydridePolymer-supported cyanoborohydridePolymer-bound tributylphosphane in combinationwith sodium borohydrideEnantioselective polymer-bound catalystin Corey-Itsuno procedure

Reductive aminationPolymer-supported borohydride

Reduction of nitro-groupsPolymer-supported borohydride

Dehalogenation and DesoxygenationPolymer-bound tin-hydrides

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NH CrO3X

OH

PPH2

3

RhCl

H

O

H2, xylene, 100 °C, 12h, 80%

O

OHOH

HH

HH

HON

N

NH2

O

NMe3BH4

NMe3 IO4

O

OHOH

HH

HH

HON

N

NH2

O

H2O, 79%

ApplicationsCombinations of different PSR

One-pot cleavage reaction of 1,2-diols to primary alcohols

A two step process involving alcohol oxidation and concurrent alkene reduction:

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Natural products via supported reagentsSynthesis of epimaritidine

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PSR in library generation

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polymer-supported nitrite reagent

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Steven V. Ley, J.Chem.Soc.; Perkin Trans. 1, 2000, 3815-4195Steven V. Ley, J. Chem.Soc.; Perkin Trans. 1, 1999, 1251-1252

Bannwarth W. and Felder E. (eds.): Combinatorial chemistry, A Practical Approach, Wiley-VCH, Weinheim, 2000

Literature