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Solid phase cosolvents: Polymer analogs of N,N-Dialkylcarboxamides as catalysts in nucleophilic displacement reactions
121 Soluble polymers 1 serve as effective phase transfer catalysts for several reactions under liquid-liquid biphase conditions. The catalytic activity of copolymers containing styrene units is higher than that of homopolymers. It was found that these polymers extract alkali metal cations more efficiently than their monomeric analogues, and that the extraction ability increases with increasing density of active sites, suggesting a cooperative effect of active sites. It is reasonable therefore to assume that the catalytic activity is due to both cation extraction ability of polymers and the activation of anions caused by desolvation in the hydrophobic regions of polymers. Insoluble polymers II also worked as phase transfer catalysts. Published in Pure Appl. Chem., 60 (1988) 387.
Asymmetric Hydroformylation Catalyzed by Polymer-supported Chiral Platinum Complexes G. Parrinello, Ciba-Geigy, Fribourg, Switzerland and J.K. Stille, Colorado State University, Fort Collins, CO, U.S.A. The polymer-supported chiral complexes 1 and 2, in the presence of stannous chloride, catalyzed the asymmetric hydroformylation of a variety of prochiral olefins. The hydroformylation of styrene in the presence of 1 afforded the corresponding aldehyde in 56-65% enantiomeric excess (ee). Higher ee's (70-80%) were achieved in the presence of catalyst 2, but racemization of the product was observed under the reaction conditions. When the latter reaction was carried out in the presence of triethyl orthoformate, an enantiomerically pure metal was obtained. The catalysts could be recovered and reused with slight loss in rate but no loss in selectivity.
l a (x : O) l b (x = 0 . 1 ) Published in J. Amer. Chem. Soc., 104 (1987) 7122.
Solid Phase Cosolvents: Polymer Analogs of N,N-Diaikylcarboxamides as Catalysts in Nucleophilic Displacement Reactions V. Janout and J. Kahovec, Czechoslovak Academy of Sciences, Prague, Czechoslovakia Functional polymers with bound groups imitating the structure of polar aprotic solvents are effective catalysts of organic reactions. It is known that N,N-disubstituted carboxamides are a suitable reaction medium in which some organic reactions become considerably accelerated.
122
@--CH2R
I :
R =
--(NCH2CH2)n
( n:
2--7)
I
COCH 3 "IT:
R =
--N(CH3)COCH 3
I][I :
R =
--N(CH2)3"-I
\coZJ "l~': R :
--N(CH2)5"~I
'V :
\co
R :
--N(CH2)7'~ ~
"co--]
A series of functional polymers I - V was prepared starting from commercially available polymers. Their activity as solid-phase cosolvent was tested in the nucleophilic displacement reactions in 1-bromooctane with alkali iodides and thiocyanates carried out under L - S - L triphase catalysis conditions (toluene-polymer-water) and with alkali phenoxides under L - S two-phase conditions (polymer-dioxane). Activity of these polymer catalysts is considerably affected by the degree of substitution and the type of polymer matrix and functional group, while the effect of the cumulation of functional groups is not so pronounced. The influence of polymer carrier and complexing ability of functional polymers on the catalytic activity is discussed. Not intended for publication.
Oxidative Properties of Polymer Bonded Sulfoxides E. Y a a c o u b , J . L . F o u r e y s , A . R e v i l l o n a n d P. L e P e r c h e ¢ , C.N.R.S. - Laboratoire des Mat6riaux
Organiques BP 24, Vernaison, France Activated copolysulfoxides display oxidative properties towards alcohol derivatives. Selective oxidation of structurally diverse alcohols into aldehydes has been performed at room temperature using a stoichiometric part of activated copolysulfoxide-electrophile complexes. Maximum activity was obtained for compositions which can be correlated to optimal hydrophobic-polar effects. Moreover, profound changes in reactivity have been obtained depending on whether soluble or crosslinked polymers of various morphologies are involved, such as in the case of copolysulfoxide-trifluoromethylacetic anhydride and carbodiimide complexes. Examples are discussed in order to illustrate the scope and limitations of the use of such activated soluble and crosslinked copolysulfoxides in the oxidation of alcohols. To be published in Reactive Polymers (in press).
Problems Arising in the Synthesis of Highly Loaded Polymer-supported Macropolycyclic Ligands Silvio Quici, Fernando
Montanari
a n d P i e r L u c i o A n e l l i , University of Milan, Milan, Italy
Our previous investigation on factors ruling phase-transfer catalytic activity of polymer-supported quaternary onium salts and crown ethers demonstrated that the percent of ring substitution (p.r.s.) strongly influences a number of parameters: swelling, water content, diffusion rates, and, in the case of crown ethers, the extent of complexation, among others. A combination of all these parameters determines the overall efficiency of the bonded catalyst. In order to extend this study to more sophisticated phase-transfer catalysts (cryptands, cylindranes, etc.), the synthesis of a homogeneous series of immobilized cryptands in a wide range of loading was undertaken. Reaction of hydroxymethyl [2.2.2.]cryptand and lightly loaded ehloromethylpolystyrenes ( < 1 meq of C1/g) afforded polymer-supported cryptands 1, which are highly efficient catalysts in anion-promoted reactions carried out under phase transfer conditions.
Asymmetric Hydroformylation Catalyzed by Polymer-supported Chiral Platinum Complexes G. Parrinello, Ciba-Geigy, Fribourg, Switzerland and J.K. Stille, Colorado State University, Fort Collins, CO, U.S.A. The polymer-supported chiral complexes 1 and 2, in the presence of stannous chloride, catalyzed the asymmetric hydroformylation of a variety of prochiral olefins. The hydroformylation of styrene in the presence of 1 afforded the corresponding aldehyde in 56-65% enantiomeric excess (ee). Higher ee's (70-80%) were achieved in the presence of catalyst 2, but racemization of the product was observed under the reaction conditions. When the latter reaction was carried out in the presence of triethyl orthoformate, an enantiomerically pure metal was obtained. The catalysts could be recovered and reused with slight loss in rate but no loss in selectivity.
l a (x : O) l b (x = 0 . 1 ) Published in J. Amer. Chem. Soc., 104 (1987) 7122.
Solid Phase Cosolvents: Polymer Analogs of N,N-Diaikylcarboxamides as Catalysts in Nucleophilic Displacement Reactions V. Janout and J. Kahovec, Czechoslovak Academy of Sciences, Prague, Czechoslovakia Functional polymers with bound groups imitating the structure of polar aprotic solvents are effective catalysts of organic reactions. It is known that N,N-disubstituted carboxamides are a suitable reaction medium in which some organic reactions become considerably accelerated.
122
@--CH2R
I :
R =
--(NCH2CH2)n
( n:
2--7)
I
COCH 3 "IT:
R =
--N(CH3)COCH 3
I][I :
R =
--N(CH2)3"-I
\coZJ "l~': R :
--N(CH2)5"~I
'V :
\co
R :
--N(CH2)7'~ ~
"co--]
A series of functional polymers I - V was prepared starting from commercially available polymers. Their activity as solid-phase cosolvent was tested in the nucleophilic displacement reactions in 1-bromooctane with alkali iodides and thiocyanates carried out under L - S - L triphase catalysis conditions (toluene-polymer-water) and with alkali phenoxides under L - S two-phase conditions (polymer-dioxane). Activity of these polymer catalysts is considerably affected by the degree of substitution and the type of polymer matrix and functional group, while the effect of the cumulation of functional groups is not so pronounced. The influence of polymer carrier and complexing ability of functional polymers on the catalytic activity is discussed. Not intended for publication.
Oxidative Properties of Polymer Bonded Sulfoxides E. Y a a c o u b , J . L . F o u r e y s , A . R e v i l l o n a n d P. L e P e r c h e ¢ , C.N.R.S. - Laboratoire des Mat6riaux
Organiques BP 24, Vernaison, France Activated copolysulfoxides display oxidative properties towards alcohol derivatives. Selective oxidation of structurally diverse alcohols into aldehydes has been performed at room temperature using a stoichiometric part of activated copolysulfoxide-electrophile complexes. Maximum activity was obtained for compositions which can be correlated to optimal hydrophobic-polar effects. Moreover, profound changes in reactivity have been obtained depending on whether soluble or crosslinked polymers of various morphologies are involved, such as in the case of copolysulfoxide-trifluoromethylacetic anhydride and carbodiimide complexes. Examples are discussed in order to illustrate the scope and limitations of the use of such activated soluble and crosslinked copolysulfoxides in the oxidation of alcohols. To be published in Reactive Polymers (in press).
Problems Arising in the Synthesis of Highly Loaded Polymer-supported Macropolycyclic Ligands Silvio Quici, Fernando
Montanari
a n d P i e r L u c i o A n e l l i , University of Milan, Milan, Italy
Our previous investigation on factors ruling phase-transfer catalytic activity of polymer-supported quaternary onium salts and crown ethers demonstrated that the percent of ring substitution (p.r.s.) strongly influences a number of parameters: swelling, water content, diffusion rates, and, in the case of crown ethers, the extent of complexation, among others. A combination of all these parameters determines the overall efficiency of the bonded catalyst. In order to extend this study to more sophisticated phase-transfer catalysts (cryptands, cylindranes, etc.), the synthesis of a homogeneous series of immobilized cryptands in a wide range of loading was undertaken. Reaction of hydroxymethyl [2.2.2.]cryptand and lightly loaded ehloromethylpolystyrenes ( < 1 meq of C1/g) afforded polymer-supported cryptands 1, which are highly efficient catalysts in anion-promoted reactions carried out under phase transfer conditions.