Isocyanides polymers

Isocyanide polymers functionalized with amino acid groups, typically di-or tripeptides containing histidine or serine, give enantioselective deacylation and rate enhancements. Their activity is increased by addition of cationic surfactants (Visser et al., 1985). 

These poly(isocyanide) polymers form rigid, rodlike helices on the surface of water, which can be easily transferred to a solid substrate by means of the LB method. The resulting films have a Coo symmetry. 

Figure 16. Isocyanide polymer (R-N=C<)n containing benzo-18-crown-6 sidechains 12. Rigid helices with four repeating units per helical turn arrange the crown ether rings on top of each other and four channel structures are formed. ...

Isocyanide Polymers Bulky isocyanides give polymers having a 4 1 helical conformation (115) [154]. An optically active polyisocyanide was first obtained by chromatographic resolution of poly(f-butyl isocyanide) (poly-116) using optically active poly((S)-sec-butyl isocyanide) as a stationary phase and the polymer showing positive rotation was found to possess an M-helical conformation on the basis of CD spectral analysis [155,156]. Polymerization of bulky isocyanides with chiral catalysts also leads to optically active polymers. 

Isocyanide Polymers Optically active polyisocyanides with excess helix sense are obtained from optically active monomers by polymerization with NiCI-,. The polymers obtained from (R)-(CH3)2CHCH(CH,)NC, (fl)-(CH3)2CHCH2CH(CH3)NC, and (R)-n-C6H13CH(CH3)NC have M helical sense with screw-sense excesses of 62%. 56%, and 20%, respectively [189]. The copolymerization of achiral phenyl isocyanide with optically active... 

Covalent bonding Tyrosine-based isocyanide polymer 4-(3-Br-n-propoxy)phenyl-substituted porphyrin van der Made et al. (117)... 

Ex(30) values show a good, often linear, correlation with a large number of other solvent sensitive processes, such as reaction rates and shifts of chemical equilibria. The betaine dye (Scheme 3) and specially designed derivatives are useful molecular probes in the study of micellar interfaces, microemulsions and phospholipid bUayers, of rigid rod-Uke isocyanide polymers, and the retention behaviour in reversed-phase chromatography. In addition to its solvatochromic behaviour, the dye is sensitive to temperature ( thermosolvatochromism ) and pressure changes ( piezosolvatochromism ) and also to the presence of electrol)d es ( halosolvatochromism ). 

An alternative approach towards the PASP synthesis of isocyanides was developed by Bradley [100,101]. It involved the use of a polymer-supported sul-fonyl chloride in the presence of base to afford the dehydration of formamides (Scheme 21). The formamides required could be easily prepared by reaction of the corresponding amines with a formylated benzotriazole resin. Opti-... 

In the reaction of Ni(CNBu )4 and methyl iodide oligomerization of the isocyanide was observed the only isolable nickel complex was (I), shown below. This product is believed to arise through sequential insertions of three isocyanides into a nickel-carbon bond. Upon further treatment with additional isocyanide at a temperature greater than 60° C one obtains a polymer (RNC) presumably through multiple isocyanide insertion reactions. The addition of benzoyl chloride to Ni(CNBu )4 gave two isolable compounds Ni(CNBu )3(COPh)Cl (74%) and (II) (8.2%). This latter reaction, and the isolation of (II) in particular, suggests that the proposed mechanism for polymerization of isocyanides is reasonable. 

A novel polysiloxane, containing the isocyanide group pendent to the backbone, has been synthesized. It is observed to react with the metal vapors of chromium, iron and nickel to afford binary metal complexes of the type M(CN-[P])n, where n = 6, 5, 4 respectively, in which the polymer-attached isocyanide group provides the stabilization for the metal center. The product obtained from the reaction with Fe was found to be photosensitive yielding the Fe2(CN-[P])q species and extensive cross-linking of the polymer. The Cr and Ni products were able to be oxidized on exposure of thin films to the air, or electrochemically in the presence of an electron relay. The availability of different oxidation states for the metals in these new materials gives hope that novel redox-active polymers may be accessible. 

We shall focus here on the synthesis of the isocyanide-containing polymer. Several reactions of the polymer with the metal vapors of Cr, Fe and Ni using a matrix-scale modeling technique, as well as synthetic-scale metal vapor methods, are then presented in order to demonstrate the reactivity of the isocyanide groups on the polymer. Finally, preliminary studies of the reactivity of the polymer-based metal complexes are described. 

The procedure described here is not limited to the preparation of polymers such as 2. Starting from the difunctional silane 3 we have synthesized a copolymer, poly(dimethyl-co-isocyanopropylmethyl-siloxane) > as well as a linear homopolymer, poly(isocyanopropyl-methylsiloxane) 8 (Scheme 2). Indeed, preparation of a monofunctional analogue of 2. and h creates the potential for end-capping with an isocyanide function any polymer containing other functional groups, thereby in principle permitting mixed ligand complexes of polymers to be accessed. 

Focusing on reactions using the Fluid Matrix Technique, we have studied the interaction of chromium vapor with 2 at 200 K (13). The resulting film was found to contain metal complexes encapsulated within the polymer in which the isocyanide group adopts a well-defined octahedral arrangement around the chromium center, i.e. a species of type Cr(CN-[P])g. Since characterization of this metal complex within the polymer is not trivial we shall develop the analysis in a little detail. 

Diethynyl-pyridine was reacted with 2 equiv. of (Me2S)AuCl to give a gold alkynyl as an insoluble coordination polymer of unknown structure. This product could be dissolved in organic solvents with cBuNG to afford the bis(isocyanide) complex with an angular structure (Scheme 50).214... 

The material system is a Langmuir-Blodgett film of the S enantiomer of a chiral polymer deposited on a glass substrate. The polymer is a poly(isocyanide)30 functionalized with a nonlinear optical chromophore (see Figure 9.14). In this particular system the optical nonlinearity and chirality are present on two different levels of the molecular structure. The chirality of the polymer is located in the helical backbone whereas the nonlinearity is present in the attached chromophores. Hence, this opens the possibility to optimize both properties independently. 

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