Amines with anhydrides

I perirnemal Procedure 13.1 Typical acylation of support-bound amines with anhydrides formed in situ [71 ]... 

Details about the acylation of amines with anhydrides and acid chlorides are in L. M. Harwood, C. J. Moody, and J. M. Percy, Experimental Organic Chemistry, 2nd edn, Blackwell, Oxford, 1999, p 279. 

Organosilicon aminoacids and their ammonium salts are obtained by interaction of amines with anhydrides of unsaturated dicarboxylic acids (maleic, phthalic, 3-methyltetrahydrophthalic). Thus, from the reaction of 3-aminopropyltriethoxysilane with maleic anhydride, for example, a neutral product IV was obtained, which according to NMR spectroscopy data is an ammonium salt (Eq. 3 and Fig. 1). 

Figure 5.1 Reaction of amine with anhydride to form an imide.

Acylation of amines by anhydrides may show autocatalytic behaviour. Thus the reaction of various amines with anhydrides in benzene is catalysed by the monomeric form of the acid produced . Litvinenko has suggested that the catalytic effect is due to complex formation (7 or 8) and the catalytic power of the carboxylic acid increases with acid strength until protonation of the amine occurs. Similar complexes have been proposed for the add-catalysed acylation... 

Amides are readily prepared by acylation of ammonia and amines with acyl chlorides acid anhydrides or esters... 

Section 20 14 Amides are normally prepared by the reaction of amines with acyl chlo rides anhydrides or esters... 

Rea.ctlons, As with other tertiary alcohols, esterification with carboxyUc acids is difficult and esters are prepared with anhydrides (181), acid chlorides (182), or ketene (183). Carbamic esters may be prepared by treatment with an isocyanate (184) or with phosgene followed by ammonia or an amine (185). 

The resulting bisepoxy compounds are cross-linked cold with polyamines, if necessary with added accelerators. A hot cure can either be accomphshed with amines or anhydrides (eg, phthaUc acid anhydride). If suitable initiators are present, EP systems can also be cross-linked by radiation. 

The free maleic acid content in maleic anhydride is determined by direct potentiometric titration (166). The procedure involves the use of a tertiary amine, A/-ethylpipetidine [766-09-6J, as a titrant. A tertiary amine is chosen as a titrant since it is nonreactive with anhydrides (166,167). The titration is conducted in an anhydrous solvent system. Only one of the carboxyhc acid groups is titrated by this procedure. The second hydrogen s dissociation constant is too weak to titrate (166). This test method is not only used to determine the latent acid content in refined maleic acid, but also as a measure of the sample exposure to moisture during shipping. 

The reverse reaction is an intramolecular acidolysis of amide group by the o-carboxyhc acid to reform anhydride and amine. This unique feature is the result of an ortho neighboring effect. In contrast, the acylation of an amine with ben2oic anhydride is an irreversible reaction under the same reaction conditions. The poly(amic acid) stmcture (8) can be considered as a class of polyamides. Aromatic polyamides that lack ortho carboxylic groups are very... 

Applications. Epoxy resias constitute over 90% of the matrix resia material used ia advanced composites. In addition, epoxy resias are used ia all the various fabrication processes that convert resias and reinforcements iato composite articles. Liquid resias ia combiaation, mainly, with amines and anhydride are used for filament winding, resia transfer mol ding, and pultmsion. Parts for aircraft, rocket cases, pipes, rods, tennis rackets, ski poles, golf club shafts, and fishing poles are made by one of these processes with an epoxy resia system. 

The bisphenol A-derived epoxy resins are most frequendy cured with anhydrides, aUphatic amines, or polyamides, depending on desired end properties. Some of the outstanding properties are superior electrical properties, chemical resistance, heat resistance, and adhesion. Conventional epoxy resins range from low viscosity Hquids to soHd resins. 

The simplest method for acetamide preparation involves reaction of the amine with acetic anhydride or acetyl chloride with or without added base. Some other methods are listed below. 

In turn the oxazoline-containing polymer may then react very rapidly (e.g. at 240°C) with such groups as carboxyls, amines, phenols, anhydrides or epoxides, which may be present in other polymers. This reaction will link the two polymers by a rearrangement reaction similar to that involved in a rearrangement polymerisation without the evolution of water or any gaseous condensation products (Figure 7.14). 

Reaction of amines with acyl chlorides (Section 20.4) Amines are converted to amides on reaction with acyl chlorides. Other acylating agents, such as carboxylic acid anhydrides and esters, may also be used but are less reactive. 

These Br nsted-type plots often seem to be scatter diagrams until the points are collated into groups related by specific structural features. Thus, p-nitrophenyl acetate gives four separate, but parallel, lines for reactions with pyridines, anilines, imidazoles, and oxygen nucleophiles.Figure 7-4 shows such a plot for the reaction of trans-cmmm c anhydride with primary and secondary aliphatic amines to give substituted cinnamamides.All of the primary amines without substituents on the a carbon (R-CHi-NHi) fall on a line of slope 0.62 cyclopentylamine also lies on this line. If this line is characteristic of normal behavior, most of the deviations become qualitatively explicable. The line drawn through the secondary amines (slope 1.98) connects amines with the structure R-CHi-NH-CHi-R. The different steric requirements in the acylation reaction and in the model process... 

Figure 7-4. Br nsted-type plot for reaction of aliphatic amines with cinnamic anhydride at 25°C in acetonitrile "" the pK values are for the conjugate acids in water. Open circles primary amines closed circles secondary amines.

The 4-nitro-A -phthalimide, prepared by heating the amine with the anhydride to 130° for 30 min, is cleaved with MeNHCH2CH2NH2 (71-92% yield). These cleavage conditions were compatible with cephalosporins, where the phthalim-ide was removed in 92% yield at —50° in 30 min. ... 

Nucleophilic aromatic substitution of the anion from ary lace ton itrile 113 on the dichloroni-trobenzene 114 results in replacement of the para halogen and formation of 115. Reduction of the nitro group gives the corresponding aniline (116). Acylation of the amine with 3,5-diiodoacetylsa-licylic acid 117 by means of the mixed anhydride formed by use of ethyl chloroformate, gives, after alkaline hydroly.sis, the anthelmintic agent closantel (118) [28]. 

Bourgeois et al. reported a new approach227 wherein poly(arylene ether sulfone) and poly(arylene ether ketone) were functionalized with anhydride and amine chain ends, respectively, to afford imide-linked copolymers. 

For all the reactions with anhydrides it is preferable to use the free amine rather than the hydrochloride salt in order to reduce the amount of external base in the reaction mixture and thus obtain clean products. 

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