Diamines aromatic, basicity

The same reaction has been studied with aromatic and aliphatic diamines, and the conclusion has been drawn that the procedure is only valid for aliphatic diamines, because the low basicity of aromatic diamines does not allow for polymer formation in mild conditions. 

This scheme eliminates the process of converting bis(etherimide)s to bis(ether anhydride)s. When polyetherimides are fusible the polymerization is performed in the melt, allowing the monamine to distill off. It is advantageous if the amino groups of diamines are more basic or nucleophilic than the by-product monoamine. Bisimides derived from heteroaromatic amines such as 2-arninopyridine are readily exchanged by common aromatic diamines (68,69). High molecular weight polyetherimides have been synthesized from various N,lSf -bis(heteroaryl)bis(etherimide)s. 

Fibers in which the basic chemical units have been formed by chemical synthesis, followed by fiber formation, are called synthetic fibers. Examples include nylon, carbon, boron fibers, organic fibers, ceramic fibers, and metallic fibers. Among all commercially available fibers, Kevlar fibers exhibit high strength and modulus. (Kevlar is a DuPont trademark for poly [p-phenylene diamine terephthalamide].) It is an aromatic polyamide (aramid) in which at least 85% of the... 

The polymerization of aromatic diamines with acid chlorides in solution works well.7 914 35 The basicity of the aromatic diamine is low and acid binding can be achieved with several compounds and even solvents such as TV-methylpyrrolidonc (NMP) and dimethylacetamide (DMAc). The all-para aromatic amide poly(p-phenyleneterephthalamide) can be synthesized in DM Ac.7,9,14 To prevent precipitation of the polymer, a salt such as calcium chloride or lithium chloride can be added. It is also possible to react the acid chloride with a silylated diamine ... 

This reaction is simple and qualitative36 37 the diamine can be both an aromatic and an aliphatic diamine. With this method, even star-shaped PAs have been synthesized.37 Solution polymerization from acid chlorides and aliphatic diamines is more difficult due to the strong basicity of the aliphatic amine groups. Acid binders which have been used with aliphatic diamines are the tertiary amines with high kb values these include dimethylbenzylamine and diisopropylethylamine.4 38... 

Similarly, the reaction of nitro compounds with the M-Boc aromatic imines 86 occurred in the presence of the enantiopure protic catalyst 87, which is a white, crystalline bench-stable salt [52] (Scheme 15). The reactions of ni-tromethane, very slow at - 20 °C, were accelerated in the presence of 10 mol % of 87, and the /3-amino compounds 88 were obtained with moderate yields and moderate to high enantioselectivities. Positive results were also obtained in the corresponding reactions of nitropropane to give the products 90. Hence, the primary diamines 89 and 91 are available by this route, which is advantageous for the significantly lower cost and toxicity of the catalyst and its easy removal from the reaction mixture simply by a basic wash. These results should stimulate further research on the development of new acid-catalyzed systems. 

An additional modification in the above synthetic scheme is possible by introducing the aromatic diamine in the form of its trimethylsilyl derivative [72]. Monotrimethylsilyl-substituted amines are readily prepared from the free amine with hexamethyldisilazane or trimethylsilyl chloride in the presence of a tertiary amine [73, 74] whereas bis(trimethylsilyl)-substituted amines require more aggressive reagents, such as butyllithium in conjunction with trimethylsilyl chloride [75]. As illustrated in Scheme 19, monotrimethylsilyl-substituted amines react with acyl chlorides to form the corresponding amides and liberate trimethylsilyl chloride. Monotrimethylsilyl-substituted amines are reported to display increased reactivity with acyl chlorides [76], This is of great synthetic importance since the increased reactivity allows for reaction with low basicity amines. Bis(trimethylsilyl)-substituted amines, on the other hand, react with acyl chlorides to form the corresponding JV-trimethylsilyl amides, see Scheme 20. The JV-trimethylsilyl amides are much more soluble in common organic solvents. However, they are hydrolytically unstable and readily convert back to the free amides. 

Microwave-assisted organic synthesis may also be used for carrying out the multicomponent reactions of ketones and 1,2-diamines [20, 21, 92, 100]. For example, the three-component reaction of o-PDA 1 with acetoacetic acid ethyl ester 83 and a series of aromatic and heteroaromatic aldehydes 84 proceeds under microwave irradiation with very high yields of diazepines 85 (up to 95%) [100]. Reaction of 2 equiv of cyclohexanone 86 with o-PDA 1 was also realized in a microwave field on a basic alumina surface in 4 min [92] (Scheme 4.27). 

The solubility of these dyes is significantly enhanced by introduction of alkenyl [35], hydroxypropyl [36], or polyetheralkyl [37] moieties into the trialkylammonium group. The trialkylammonium group may also be a component of a heterocyclic ring [38], When the trialkylammonium residue contains an alkyl chain of more than 11 carbon atoms, the dyes become soluble in aliphatic and alicyclic hydrocarbons and can be used for the production of printing inks [39], With aromatic diamines as the diazo components, such as 4,4 -diaminodiphenyl sulfone, basic disazo dyes are obtained which are suitable for dyeing acid-modified polyamide materials [40],... 

This first step would involve the displacement of a pyridine ligand by the aromatic amine. Some evidence points to this being the rate-determining step. A strict positive correlation between the basicity of the diamine relative to pyridine and the oxidative coupling rate (as measured by the oxygen absorption) was established (3). 

Examples of aromatic amines that can be dia-zotized are shown in Fig. 13.83. This extremely abbreviated list is designed to show that a wide variety of amines can be used, including hydrophobic, weakly basic, hydrophilic, and heterocyclic compounds. orf/zo-Diamines are not typically used because of their propensity to undergo triazole formation (Fig. 13.84). 

All industrial polyurethane chemistry is based on only a few types of basic isocyanates. The most significant aromatic diisocyanates are TDI and MD. TDI is derived from toluene. This is initially nitrated to dinitrotoluene, then hydrogenated to diamine, and finally phosgenated to diisocyanate. A defined mixture of isomers comprising toluene-2,4-and 2,6-diisocyanate is obtained. Approximately 1.3 million tons/year of TDI are produced world-wide, most of which is used in the production of polyurethane flexible foam materials. 

A CSP based on the analogues 3,5-dinitrobenzoylated 1,2-diphenylethane-1,2-diamine (DNB-DPEDA) (see Fig. 9.26a) [349-353] has been commercialized by Regis under the tradename Ulmo. This CSP has proven to be excellent for the direct separation of aryl alcohol enantiomers without derivatization (see Fig. 9.26b) [349,351]. This improved Pirkle-concept CSP, that contains also ir-acidic as well as moderate n-basic aromatic binding sites, nicely resolved a wide variety of chiral drugs [350] and compounds of pharmaceutical interest [352]. 

It was observed that the ethylenediamine derivative (33a) and its metal complexes undergo hydrolysis in strongly acidic dmso-water 80 20 wt/wt media, induced by the highly basic character of the nitrogen atoms of the aliphatic diamine.126,127 However, solutions in neutral or basic conditions were found to be stable. In contrast, (33q) and (33r), derived from o-phenylenediamine and m-phenylenediamine respectively, do not hydrolyze at pH higher than 2.5.123 124 128 The greater difficulty in protonating aromatic diamines compared to aliphatic diamines is believed to be responsible for the stability of these SBs and their complexes in acidic dmso-water solution. 

The reaction of carbon disulfide with 1,2-alkylene diamines (I) yields N-(2-aminoethyl) dithiocarbamic acids (II) which split off hydrogen sulfide thermally to give imidazolidine-2-thiones (III) (Hofmann-process). The simplest example, the reaction of carbon disulfide with ethylenediamine, is described in Organic Synthesis (5). The reaction is general for N,N -dialkyl-, N,N -diaryI, as well as for N,N -bis-(arylakyl) ethylene diamines. The rate of reaction is determined by the basicity of the diamine. Electron-donor substituents in the para-position of N-aromatically substituted ethylene diamines accelerate dithiocarbamate formation electron-acceptor groups retard it. 

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