Acid Anhydrides to Imides

MDA reacts with acid anhydrides to form amides. In the reaction with maleic anhydride both of the amino hydrogens are replaced to form the imide, A[,Ar-(methylenedi-/)-phenylene) dimaleimide [1367-54-5]... 

Pyrrole is one of the most prominent heterocycles, having been known for more than 150 years, and it is the structural skeleton of several natural products, synthetic pharmaceuticals, and electrically conducting materials. A simple access to the pyrrole ring system involves the conversion of cyclic anhydrides into five-membered imides. Mortoni and coworkers have described the conversion of 2-methylquinoline-3,4-dicarboxylic acid anhydride to a quinoline-3,4-dicarboximide library by treatment of the anhydride with a diverse set of primary amines under microwave conditions (Scheme 6.180) [341]. The authors studied a range of different conditions, including dry media protocols (see Section 4.1) whereby the starting materials were adsorbed onto an inorganic support and then irradiated with microwaves. For the transforma-... 

The addition of alcohols to nitrilium salts gives rise to formation of alkoxymethyleneiminium salts, which react with bases to yield imido esters (231 Scheme 33). - By deprotonation of carboxylic acid amides ambident anions are formed, which can be alkylated in the presence of silver ions to give imido esters, e.g. (232). " Secondary amides react with trifluoroacetic acid anhydride or trifluorosulfonic acid anhydride to give mixed anhydrides of imidic acids (233). ... 

Functionalized PPE may he prepared hy allowing PPE to react with a species that contains both a C=C bond and a reactive moiety, such as hydroxyl, acid, anhydride, amine, imide, epoxy, etc. Examples of species of the acid and anhydride type include maleic anhydride, fumaric acid, and citraconic anhydride. ... 

Lactones and anhydrides each react with ammonia or amines to give nitrogen derivatives. In some cases, lactones are converted to lactams and anhydrides to imides. In these cases, hydrolysis will open the ring and generate an amino acid (see... 

The reactions of primary amines and maleic anhydride yield amic acids that can be dehydrated to imides, polyimides (qv), or isoimides depending on the reaction conditions (35—37). However, these products require multistep processes. Pathways with favorable economics are difficult to achieve. Amines and pyridines decompose maleic anhydride, often ia a violent reaction. Carbon dioxide [124-38-9] is a typical end product for this exothermic reaction (38). 

Naphthalenedicarboxylic Acid. NaphthaUc acid readily dehydrates on heating to 1,8-naphthalenedicarboxyhc acid anhydride [81-84-5] (naphthahc anhydride) (41). The anhydride and its imide naphthaUmide [81-83-4] (R = H) (42) are intermediates for important dyes, pigments, optical bleaches, and biologically active compounds. 

Fig. 2. Cyclization of amic acid to imides or isoimides via (12). Formation of the mixed anhydride intermediate (12) is shown in text.

Reaction of anthanilic acid 112 with acid anhydrides afforded the corresponding imide derivatives 113. Subjecting 113 to intramolecular Wittig cyclization has been achieved by treatment with A-phenyl(triphe-nylphosphoranylidene)etheneimine in toluene or dioxane whereby the corresponding pyrroloquinolines 116 were obtained (94TL9229). The intermediate 115 resulting from the rearrangement of 114 could be isolated when the reaction was done at room temperature (Scheme 22). 

In comparison, no structural modification of model B was seen before 120 h of aging (80 °C). However, after 120 h two small doublets appeared in the NMR spectrum and several additional peaks became noticeable in the NMR spectrum. It was determined by NMR and IR spectroscopy that the hydrolysis products were an imide/carboxylic acid and an imide/anhydride. Model B was then aged for 1200 h at 80 °C to quantitatively determine the amount of hydrolysis products as a function of time. The relative intensity of the peaks due to carboxylic acid is constant after some time. The authors suggest that an equilibrium occurs between model B and the products formed during hydrolysis, and therefore, the conversion to hydrolysis products is limited to about 12%. This critical fraction is probably enough to cause some degradation of polymeric materials, but research on six-membered polyimides has remained active. 

Monomers 111 (a -d), were prepared from the common starting material 15 by a potassium phenate displacement of the aromatic nitro group. The yields of the keto-ether amine products ranged from 90 to 100% and were of sufficient purity after extractive work up to be utilized directly in the synthesis of the various maleimide monomers. Imidization of the aminobenzocyclobutenes was accomplished using standard reaction conditions (maleic anhydride to form the amic acid followed by cyclodehydration with acetic anhydride and triethyla-mine) and provided the maleimide products in yields ranging from 60 to 90%. 

Initially, water can cause the hydrolysis of the anhydride or the isocyanate, Scheme 28 (reaction 1 and 2), although the isocyanate hydrolysis has been reported to occur much more rapidly [99]. The hydrolyzed isocyanate (car-bamic acid) may then react further with another isocyanate to yield a urea derivative, see Scheme 28 (reaction 3). Either hydrolysis product, carbamic acid or diacid, can then react with isocyanate to form a mixed carbamic carboxylic anhydride, see Scheme 28 (reactions 4 and 5, respectively). The mixed anhydride is believed to represent the major reaction intermediate in addition to the seven-mem bered cyclic intermediate, which upon heating lose C02 to form the desired imide. The formation of the urea derivative, Scheme 28 (reaction 3), does not constitute a molecular weight limiting side-reaction, since it too has been reported to react with anhydride to form imide [100], These reactions, as a whole, would explain the reported reactivity of isocyanates with diesters of tetracarboxylic acids and with mixtures of anhydride as well as tetracarboxylic acid and tetracarboxylic acid diesters [101, 102]. In these cases, tertiary amines are also utilized to catalyze the reaction. Based on these reports, the overall reaction schematic of diisocyanates with tetracarboxylic acid derivatives can thus be illustrated in an idealized fashion as shown in Scheme 29. 

The key to acetylene terminated polyimides is the availability of the end-capper which carries the acetylene group. Hergenrother (130) published a series of ATI resins based on 4-ethynylphthalic anhydride as endcapping agent. This approach first requires the synthesis of an amine-terminated amide acid prepolymer, by reacting 1 mole of tetracarboxylic dianhydride with 2 moles of diamine, which subsequently is endcapped with 4-ethynylphthalic anhydride. The imide oligomer is finally obtained via chemical cyclodehydration. The properties of the ATI resin prepared via this route are not too different from those prepared from 3-ethynylaniline as an endcapper. When l,3-bis(3-aminophenox)benzene was used as diamine, the prepolymer is completely soluble in DMAc or NMP at room temperature, whereas 4,4 -methylene dianiline and 4,4 -oxydianiline based ATIs were only partially soluble. The chemical structure of ATIs based on 4-ethynylphthalic anhydride endcapper is shown in Fig. 45. 

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