Polymer-supported amine

Polymer-NH(CH2),NH2, (jc = 2, 4, 6), BuOH, 85°, 92-96% yield. The polymer-supported amine helps in the final purification of oligosacchar-rides that have used the TCP group for —NH2 protection. ... 

As for the solid support, several polymer-supported amines were tested (Fig. 2). For either the pyrazole and isoxazole synthesis, the best results were given by aniline-functionalized cellulose, which has also the advantage of a relatively low cost. For the 2-aminopyrimidine library, polystyrene-based piperazine and piperidine gave products with a much higher purity compared with other secondary non-cyclic or primary amines, hi both cases, the resins could be reused for up to four times before degradation in their behavior was observed. This reusability could be further enhanced (up to 10 cycles for cellulose-based aniline) when the microwave-assisted protocols were used. 

Kobayashi S, Aoki Y. />-Benzyloxybenzylamine (BOBA) resin. A new polymer-supported amine used in solid-phase organic synthesis. Tetrahedron Lett 1998 39 7345-7348. 

A number of amines have been investigated for their suitability as polymerisation initiators, including aliphatic amines (such as butylamine [17] and 1,3-diaminopropane [18]), polymer supported amines (such as cross-linked aminomethyl polystyrene [CLAMPS], Fig. 1, giving rise to immobilised polyamino acids [19]) and resin-bound amines. 

Polymer-supported amine oxides 47-49 were catalytically active for the reaction of 1-bromooctane with aqueous sodium cyanide, 66). 

The catalysts were conditioned in a 1-cyanooctane/aqueous NaCN mixture for 24 h at room temperature to avoid the induction period of the reaction. Rates (converted from a weight basis to a molar basis) with catalysts 47-49 significantly decreased as the % RS increased over the range 5 % to 50 %. With equal loadings activities of the polymer-supported amine oxides decreased with decreased lipophilicity of the catalysts (49 > 48 > 47). Lipophilic character appears to be an important factor for activity of polymer-supported cosolvents. 

Finn [66] has reported that when alkenyl boronic acids are used in this process, the aminomethylphenol intermediates can undergo a further transformation to generate 2Ff-chromenes 153 (Scheme 7.20). This process can be done efficiently with catalytic amounts of dibenzylamine or the corresponding polymer-supported amine 154 to afford a variety of substituted 2H-chromenes 155-159 in one step. 

Alkyl iodides may be transformed into aldehydes by reaction with polymer-supported amine oxide reagents359. This type of reagent dramatically reduces side-reactions, compared to other traditional oxidations in solutions and usually occurs much faster and in higher yields. Oxidation with 4-dimethylaminopyridine N-oxide has also given excellent yields of aldehydes, starting from both chlorides and bromides360. 

TMSCN, TEA, 91-100% yield. K2CO3 has also been used effectively as a base. A polymer-supported amine is also an effective catalyst. ... 

Catalysis by Non-chiral Polymer-Supported Amines and Phosphines... 

Scheme 10.10 Examples of catalysis by non-chiral polymer-supported amines.

N NCS H From polymer-supported amines by treatmem with CSj/TsCl or with CSCI,.200 ... 

Based on a multi-component condensation approach related to the Doebner reaction,Gopalsamy et developed a solid-phase synthesis for this clinically useful pharmacophore. Thus, starting from Rink resin 65, acylation with the required N-Fmoc-amino acid 232 and deprotection with piperidine gave the polymer-supported amine 233 (90% yield) which was acylated with pyruvyl chloride (234). Immobilised pymvic amide 235 was refluxed with excess of preformed benzyUdene aniline 239 or alternatively condensed with an excess of an equimolecular mixture of aldehyde 236 and anilines 237. Cleavage of 238 with 45% TFA afforded compounds 240 in good yields and with high purities (>90%) (Scheme 4.3.5). 

Scheme 7.13 Application of polymer-supported amines in the Petasis borono-Mannich reaction.

Based on Mannich-type reactions of N-acryliminoacetates with silyl enol ethers, a new method for the preparation of N-acylated amino acid derivatives via nucleophilic addition to N-acrylimino ester has been developed using a polymer-supported amine and scandium catalysts (Scheme 12.5) [9]. Ethyl N-benzoyl-2-bromoglycine was used as a substrate. It could be readily converted to reactive N-acrylimino ester in situ by treatment with a base. Immobilizations of the amine and the scandium species into polymeric supports prevented loss of activity of the catalyst. The method is simple and provides a convenient method for the preparation of N-acrylated amino acid derivatives. 

Scheme 7.40 Flow Knoevenagel condensation catalyzed by polymer-supported amine.

Several polymer-supported amine catalysts were reported for continuous-flow reactions [151]. Ley and coworkers achieved a continuous-flow synthesis of 4,5-disubstituted oxazoles [152]. Their flow system consisted of two microreactors and one scavenger column, as shown in Scheme 7.41. Isocyanine and add chloride were mixed on a glass-tip microreactor to give a reactive intermediate. Progressing this combined reaction stream through a packed column of polymer-supported phos-phazene base (57) (PS-BEMP) facilitated an intramolecular cyclization yielding the... 

Ohtl995 Ohtani, N., Inoue, Y, Inagaki, Y, Fukuda, K. and Nishiyama, T., Reactions of Amino Acid Decyl Esters with Nucleophiles Catalyzed by Polymer-Supported Amine-Metal Complexes, Bull. Chem. Soc. Jpn, 68 (1995) 1669-1675. 

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