Anhydrides to imides

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). 

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

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-... 

Staubli et al. (1991) offer an in depth analysis of the effects of sequence distribution on the Tg of poly(anhydride-co-imide)s and discuss the experimental results with respect to several applicable theoretical models... 

The wide structural diversity in the tricyclic compounds considered in this chapter ensures that they have found an equally diverse range of applications. The applications previously outlined <1996CHEC-II(7)841> have continued to be important and have been further developed. Carbocyclic anhydrides and imides continue to find application for the synthesis of polymeric materials which are used extensively in microelectronics due to their excellent thermal and electrical properties <2001PP03>. Similarly, polymers containing benzobisthiazoles, benzobisoxazoles, and... 

The monomer 91 was prepared in a multistep process and the authors did not quote the yield obtained for the final product (Fig. 41). In the first step the dianhydride 87, was reacted with m-nitroaniline 88 to form the mono imide anhydride 89 without any of the bis imide product being reported. Once this material was isolated the remaining anhydride functionality was reacted with 4-aminobenzocyclobutene 60 to form the JV-benzocyclobutenyl imide, 90. The nitro group was reduced to the amine (H2,10% Pd/C) which in turn was reacted with maleic anhydride to afford the final AB monomer, 91. Polymerization of 91 was carried out in a DSC (10 °C/min to 450 °C) [14]. Monomer 91 had a melting point of 99 °C and the final homopolymer had a Tg of257 °C [14]. A TGA of the homopolymer indicated that at 508 °C the polymer suffered a 10% weight loss. 

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. 

For a review of the reactions with anhydrides and imides (and carboxylic esters, thiol esters, and amides), see Murphy Brennan Chem. Soc. Rev. 1988,17, 1-30. For a review with respect to imides, see Flitsch Schindler Synthesis... 

In cyclic anhydrides and imides, one carbonyl group is usually easily reduced thus, phthalic anhydride with H2/Ni gives phthalide (287), and phthalimides with Zn/HCl yield phthalamides (288). Indoxyl and its 0- and 5-analogues can be reduced (Zn-HOAc) to indole, etc. 

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