Carbodiimide, polystyrene-bound

Sauer and coworkers have presented the use of polystyrene-bound carbodiimide for convenient and rapid amide synthesis [124], An equimolar mixture of 1-methy-lindole-3-carboxylate, the requisite amine, and 1-hydroxybenzotriazole (HOBt) in... 

Isothioureas can be prepared on insoluble supports by S-alkylation or S-arylation of thioureas (Entry 7, Table 14.6). Further methods for the preparation of isothioureas on insoluble supports include the N-alkylation of polystyrene-bound, A/,/V -di(alkoxy-carbonyl)isothioureas with aliphatic alcohols by Mitsunobu reaction (Entry 7, Table 14.6) and the addition of thiols to resin-bound carbodiimides [7]. Resin-bound dithio-carbamates, which can easily be prepared from Merrifield resin, carbon disulfide, and amines [76], react with phosgene to yield chlorothioformamidines, which can be converted into isothioureas by treatment with amines (Entry 8, Table 14.6). The conversion of support-bound a-amino acids into thioureas can be accompanied by the release of thiohydantoins into solution (see Section 15.9). The rate of this cyclization depends, however, on the type of linker used and on the nucleophilicity of the intermediate thiourea. 

Quinazolines have also been prepared by the reaction of a polystyrene-bound phosphoranimine and isocyanates, followed by an intramolecular cyclization of the carbodiimide intermediate 4-Ferrocenylidene-l-aminoimidazolone derivatives have been obtained from p-ferrocenyl-a-azidoacrylates and isocyanates followed by condensation of the resulting carbodiimidoester with hydrazines " In a Staudinger/ aza-Wittig process and in the presence of PPh3, bimetallic ferrocenyl oxazole derivatives (23) - (26) have been formed by the reaction of a-... 

The present procedure2 describes the conversion of resin-bound, primary aliphatic amines into isothiocyanates and the conversion of the latter into 3-aminothiophenes. The generation of isothiocyanates is related to known procedures,3 in which amines are first treated with carbon disulfide and the resulting dithiocarba-mates are desulfurized by treatment with a condensing agent (alkyl chloroformates, carbodiimides, lead or mercury salts, etc.). The presence of resin-bound isothiocyanates on the polystyrene support could be qualitatively ascertained by infrared spectroscopy (KBr-pellet strong absorption at 2091 cm-1). 

A carbodiimide-grafted polystyrene resin was reacted with tetramethyl-guanidine to give an interesting biguanide structure (Scheme 13). This was assayed as a catalyst for a transesterification reaction.33 Incidentally, resin-bound guanidines are useful bases for processes involving resin capture.34... 

Figure 8 Chemiluminescent (A and B) and bioluminescent (C) detections for immobilized hybridizations of PCR product. Dg, digoxigenin Bt, biotin Ad, avidin. Procedure A [30] Biotin moiety is incorporated into PCR products during the amplification reaction, using one 5 -biotinylated primer. The product is hybridized with a Dg-labeled probe and is immobilized on streptavidin-coated magnetic beads. This capture reaction is carried out for 30 min at 37°C. A permanent magnet is used to sediment the beads during washing to remove unbound DNA. By incubation with the washed beads for 45 min at 37°C, anti-Dg antibody conjugated to HRP enzyme is bound to the Dg-labeled probe, and luminol reaction is performed for CL detection. Procedure B [31] Wells of a polystyrene microtiter plate are activated with l-ethyl-3-(3-dimethylaminopropyl)-carbodiimide, and then coated with a labeled cDNA probe complementary to an internal region of the target DNA.

Also, reaction of the aminomethyl polystyrene with cyclohexylisocyanate affords a polymer bound urea, which is converted into the carbodiimide using Ph3PBr2. Reaction of the polycarbodiimide with methanol affords an 0-alkylisourea which is used in the 0-alkylation of carboxylic acids. ... 

However, more frequently employed has been the commercial polystyrene-supported carbodiimide 5 (0.9-1.4mmolg 1), another bound variant of DCC, although showing similar reactivity. In this supported reagent the tether to the polystyrene backbone has greater activity than the N-methylene linkage present in reagent 2 (R = Cy). 

A hydantoin library of 800 compounds has been reported by Dress-mann et al. [61]. In this approach, 20 different amino acids and over 80 primary amines were incorporated. Selected amino acids were attached via their iV-terminus to hydroxymethyl polystyrene resin by using a carbamate linker. This enabled generation of the free acid resin-bound intermediates, which could then be converted to their corresponding amides by standard carbodiimide coupling reactions and excess primary amine. Concomitant... 

Aminomethylated, crosslinked polystyrenes constitute very valuable and versatile resins for a variety of applications. The amino group can be easily acylated for the introduction of spacer and linker molecules and it was also used for the synthesis of polymer-bound carbodiimides. - In Scheme 1 S.4.4, some of the most common synthetic accesses to aminomethylated polystyrenes are summarised. 

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