Amines termination reactions

This reaction is reported to proceed at a rapid rate, with over 25% conversion in less than 0.001 s [3]. It can also proceed at very low temperatures, as in the middle of winter. Most primary substituted urea linkages, referred to as urea bonds, are more thermally stable than urethane bonds, by 20-30°C, but not in all cases. Polyamines based on aromatic amines are normally somewhat slower, especially if there are additional electron withdrawing moieties on the aromatic ring, such as chlorine or ester linkages [4]. Use of aliphatic isocyanates, such as methylene bis-4,4 -(cyclohexylisocyanate) (HnMDI), in place of MDI, has been shown to slow the gelation rate to about 60 s, with an amine chain extender present. Sterically hindered secondary amine-terminated polyols, in conjunction with certain aliphatic isocyanates, are reported to have slower gelation times, in some cases as long as 24 h [4]. 

Scheme 4 Reaction scheme for the formation of graft copolymer between amine terminated NBR and modified polypropylenes.

Amine-terminated siloxane oligomers have also been utilized in the synthesis of various siloxane-amide and siloxane-imide copolymers, High molecular weight siloxane-amide copolymers have been synthesized by the solution or interfacial co-polymerization of siloxane oligomers with sebacoyl chloride or terephthaloyl chloride respectively 1S5,165). In some reactions diamine chain extenders have also been utilized. Thermal and dynamic mechanical characterization of these copolymers have shown the formation of multiphase systems160). Compression molded films displayed very good elastomeric properties. 

ABA type poly(hydroxyethyl methacrylate) (HEMA) and PDMS copolymers were synthesized by the coupling reactions of preformed a,co-isocyanate terminated PDMS oligomers and amine-terminated HEMA macromonomers312). Polymerization reactions were conducted in DMF solution at 0 °C. Products were purified by precipitation in diethyl ether to remove unreacted PDMS oligomers. After dissolving in DMF/toluene mixture, copolymers were reprecipitated in methanol/water mixture to remove unreacted HEMA oligomers. Microphase separated structures were observed under transmission electron microscope, using osmium tetroxide stained thin copolymer films. 

Synthesis and characterization of ABA type copolymers containing polydimethyl-siloxane or poly(trifluoropropyl,methyl)siloxane middle blocks and aromatic ester based liquid crystalline end blocks were reported 252,253). These materials were synthesized in solution by the reaction of primary or secondary amine-terminated, di-... 

S. V. (2007) Pd on amine-terminated ferrite nanopartides a complete magnetically recoverable facile catalyst for hydrogenation reactions. Organic Letters, 9 (7), 1419-1421. 

Acylation reactions can be done at the nucleophilic sites on pyrimidines using activated forms of carboxylic acids. Acylation of functional groups in nucleotides typically is used for protection during synthesis (Reese, 1973). However, for bioconjugate applications, the reactivity of native groups on pyrimidines is not as great as that obtained using an amine-terminal spacer derivative, such as those described in Chapter 27, Section 2.1. Yields and reaction rates are typically low for direct acylation or alkylation of pyrimidine bases, especially in aqueous environments. 

Dextran derivatives containing carboxyl- or amine-terminal spacer arms may be prepared by a number of techniques. These derivatives are useful for coupling amine- or carboxylate-containing molecules through a carbodiimide-mediated reaction to form an amide bond (Chapter 3, Section 1). Amine-terminal spacers also can be used to create secondary reactive groups by modification with a heterobifunctional crosslinking agent (Chapter 5). 

Figure 27.4 Reaction of guanine bases with N-bromosuccinimide causes bromination at the C-8 position of the ring. Amine nucleophiles can be coupled to this active derivative by nucleophilic displacement. Reaction of diamine compounds results in amine-terminal spacers that can be further modified to contain detectable components.

Figure 27.6 The 5 -phosphate group of oligonucleotides may be labeled with cystamine using the EDC/imid-azole reaction. This results in the formation of an amine-terminal spacer containing an internal disulfide group. Reduction of the disulfide provides a route to creating a free thiol for further derivatization.

Aromatic amines terminate chains in oxidizing hydrocarbons with the stoichiometric coefficient between 1 and 2 as a result of the consecutive reactions (see Chapter 15). 

The amine-terminated poly(EA) was prepared by the chain transfer polymerization of EA in the presence of the salt of aminomercaptan, followed by the reaction with carbon disulfide to give the polymeric iniferter 31. The polymerizations of St and MMA with 31 provided the triblock copolymers, poly(EA)-block-poly(St)-fcfoc/c-poly(EA) and poly(E A)-Woc/c-poly(MMA)-fcfoc/c-poly(EA), respectively, as shown in Eq. (29) [ 147] ... 

The reactions of primary amines with BENAs proceed in a more complex fashion (499, 521). In the absence of steric hindrance in the amine, terminal BENAs are readily and rapidly involved in double j3-oximino-alkylation with primary amines (Scheme 3.245, product A7)- To stop the process at the mono-alkylation step (intermediate A), a large excess of amine should be used. 

Crosslinking of amine- or hydroxy-terminated PAMAM dendrimers using cyclic anhydride - amine or cyclic anhydride - hydroxy addition reactions was employed for preparation of crosslinked thin films of very low permeability [73], Polyanhydrides, such as maleic anhydride-methyl vinyl ether copolymers, were used as crosslinking components. In the case of amine-terminated PAMAM, crosslinking and chemical stability were further increased by imidization of the maleamic acid groups retro-Michael eliminations were followed by Michael additions to further crosslink the film. 

Amine-terminated, G3 (PAMAM) dendrimer, (0.316 g 45.7 moles) was dissolved in anhydrous methyl sulfoxide (5 ml) in a 100 ml round-bottom flask flushed with dry nitrogen. After dendrimer had completely dissolved, succinic anhydride (Aldrich) (0.363 g 3.6 mmol) was added to the reaction mixture with vigorous stirring, and the mixture was allowed to react for 24 h at room temperature. The product solution was diluted with deionized water, transferred to 3500 MWCO dialysis tubing (Spectrum) and dialyzed against deionized water (18 Mil) for 3 d. The retentate solution was clarified by filtration through Whatman No. 1 filter paper, concentrated with a rotary evaporator, and lyophilized to yield a colorless powder (0.435 g, 94%). The product was analyzed by 13C-NMR, FT-IR, SEC and MALDI-MS. The analytical data were consistent with the expected carboxylic acid-terminated product. 

Amination. The synthesis of polymers with primary amine end-group functionality has been a challenge because the primary amine group can undergo rapid chain transfer and termination reactions with car-banionic chain ends (14). Schulz and Halasa (15) used a phenyllith-ium initiator with a bis(trimethylsilyl)-protected amine group to prepare amine-terminated polydienes. Nakahama and coworkers (16,17)... 

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