Reaction of potassium salts of boc amino acids with chloromethyl polystyrene catalyzed by 18-crown-6

Roeske, Roger W.; Gesellchen, Paul D.

doi:10.1016/s0040-4039(00)93047-8

Cited by 22 publications

(16 citation statements)

References 7 publications

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“…It is not clear why. Polymer-supported valine (14) gave very poor optical yields and this illustrates the importance of the P-hydroxy amine system of the cinchona alkaloids in asymmetric synthesis.…”

Section: Omementioning

confidence: 97%

“…The final weight of dried polymer was 14.821 g. The weight increase (2.821 g) corresponds to an alkaloid content of 9.60 mmol, equivalent to 0.65 mmol per g and a reaction yield of 67%. (14).-The above chloromethylated polystyrene (9.36 g, 11.8 mmol of chloromethyl groups) was treated with the potassium salt of N-t-BOC-L-valine and 18-crown-6 in dimethylformamide as described by Roeske and Gesellchen. ', The product (10.05 g) had Cl = 0% and the lack of chloromethyl groups was confirmed by i.r.…”

Section: Preparation Of Polymer-supported Catalystsmentioning

confidence: 99%

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Michael additions catalysed by cinchona alkaloids bound via their vinyl groups to preformed crosslinked polymers

Hedge¹,

Khoshdel²,

Waterhouse³

et al. 1985

J. Chem. Soc., Perkin Trans. 1

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Cinchona alkaloids have been satisfactorily bound via their vinyl groups to crosslinked polymers containing thiol residues. The products have been used to catalyse one or more of the following Michael additions: the additions of (I ) thio-p-cresol, (2) p-chlorothiophenol, and (3) thiobenzoic acid to cyclohex-2-en-1 -one, and (4) of toluene-a-thiol to 2-nitrostyrene. The steric course of reactions (1 )-( 3) is dominated by the configurations of C-8 and C-9 in the alkaloids, but the nature of the C-3 group does have an effect and this probably explains why the optical yields obtained using the polymersupported catalysts were lower than those obtained using the free alkaloids. The optical yields obtained in reaction (4), though small, did not follow this pattern. The polymers afforded higher optical yields than the free alkaloids and, in one case, the predominant enantiomer was of opposite configuration.One of the most attractive types of asymmetric synthesis is that in which chiral products are generated from achiral substrates under the influence of chiral catalysts. Polymer-supported versions of such catalysts are especially attractive.2 They are not only easily removed from the reaction product, but it may also be possible to re-use them, thereby making it economic to synthesize complex catalysts in order to achieve high enantiomeric excesses.To assess the effect of binding chiral catalysts to polymer supports we have bound cinchonidine (l), cinchonine (2), quinine (3), and quinidine (4) to crosslinked polystyrenes via their vinyl groups, and compared their catalytic properties in Michael reactions with those of the unbound alkaloids. We now report the results.

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Section: Omementioning

confidence: 97%

Section: Preparation Of Polymer-supported Catalystsmentioning

confidence: 99%

Michael additions catalysed by cinchona alkaloids bound via their vinyl groups to preformed crosslinked polymers

Hedge¹,

Khoshdel²,

Waterhouse³

et al. 1985

J. Chem. Soc., Perkin Trans. 1

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“…19,20), 18-crown-6 (Ref. 12,13,19,20), cryptand [222] (Ref. 21,22), etc., have been used in the chemical modification of polymers, few systematic studies of the influence of the catalyst on the reactions have been done.…”

Section: Choice Of Reaction Conditionsmentioning

confidence: 99%

“…12,13,16,17,19,28), nitrile (Ref. 16 The reaction can be done either in a solid-liquid-solid system, with a suspension of finely powdered base in an organic solvent containing tetrabutyl ammonium chloride or 18-crown-6, or in a liquid-solid-liquid system with a concentrated aqueous solution of …”

Section: Reactions On Chloromethyl Substituted Polystyrene (I)mentioning

confidence: 99%

Chemical Modification of Polymers Via Phase Transfer Catalysis

Fréchet

1984

Crown Ethers and Phase Transfer Catalysis in Polymer Science

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“…Parmi elles, on peut citer la protection sous forme d'esters p-trichloroethyliques2, I'emploi d'un groupe parabr~mophenacyle~ ou, dans le cas des BOC-aminoacides, I'esterification par des resines chloromethylees lors des syntheses peptidiques en phase solide du type Merrifield. 4 Dans le cadre de nos recherches sur les syntheses selectives, nous avons deja rapporte deux methodes d'introduction d'un systeme cage dans les pyrimidines, les purines et les sulfamates d'interbt biologique avec formation des derives N-alkyles correspond ant^.^ Dans ce travail, nous presentons nos resultats relatifs a la synthese d'esters carboxyliques par 0-alkylation directe d'acides aliphatiques et aromatiques, au moyen de I'adamantyl-1 bromomethylcetone (I) en utilisant tout d'abord les deux techniques de la catalyse par transfert de phase (CTP) liquide-liquide et solide-liquide, puis une methode non catalytique, a savoir I'action de quantites equimoleculaires d'agent alkylant et de triethylamine sur ces mbmes acides en solution dans I'acetone.…”

Section: Introductionunclassified

Introduction D'Un Systeme “Cage” Derive De L'Adamantane Dans Les Acides Carboxyliques, Par Alkylation En Catalyse Par Transfert De Phase Et Par Une Methode Non Catalytique

Hedayatullah

1989

Bulletin des Soc Chimique

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The syntheses of new carboxylic esters of general type RCO2‐CH2CO‐Ad (Ad=1‐adamantyl), where R may be aliphatic or aromatic, have been achieved in high yield by reaction of the corresponding acides with an appropriate derivative of adamantane under phase‐transfer conditions or by a noncatalytic procedure. The influence of the lipophilicity of the catalyst on the course of the alkylation of benzoic acide is discussed.

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Reaction of potassium salts of boc amino acids with chloromethyl polystyrene catalyzed by 18-crown-6

Cited by 22 publications

References 7 publications

Michael additions catalysed by cinchona alkaloids bound via their vinyl groups to preformed crosslinked polymers

Michael additions catalysed by cinchona alkaloids bound via their vinyl groups to preformed crosslinked polymers

Chemical Modification of Polymers Via Phase Transfer Catalysis

Introduction D'Un Systeme “Cage” Derive De L'Adamantane Dans Les Acides Carboxyliques, Par Alkylation En Catalyse Par Transfert De Phase Et Par Une Methode Non Catalytique

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