Maleimides N-substituted

Over the years many attempts have been made to produce commercial acrylic polymers with a higher softening point than PMMA. The usual approach was to copolymerise MMA with a second monomer such as maleic anhydride or an N-substituted maleimide which gave homopolymers with a higher Tg than PMMA. In this way copolymers with Vicat softening points as high as 135°C could be obtained. 

The original compound, maleimide (2,5-dioxo-A -pyrroline), is synthesized by the cyclo-condensation of ammonia and maleic acid. Similarly, primary amine is added to maleic anhydride, followed by cyclocondensation, to form N-substituted maleimide (Fig. 2). This reaction is applied to the preparation of bis-maleimides (BMl) [1]. At first, BMI was used as a crosslinking agent for natural rubber (NR). An o-dichlorobenzene solution of NR was crosslinked by BMI at I08-150°C in the presence of peroxides. The radicals generated from peroxides react with the double bonds of both BMI and NR [ 1 ]. 

Pyridinium p-toluenesulfonylmethylide 91 has been used as a formyl anion equivalent for conjugate addition to N-substituted maleimides to give the enol ethers 92, which were readily deprotected to give the aldehydes 93 (80TL705). 

Isatin derivatives and proline react to give stereospecific formation of an azo-methine ylide intermediate via the decarboxylation route. The resulting 1,3-dipole undergoes a cycloaddition reaction with N-substituted maleimide (6), as a dipolaro-... 

Few examples on the reactivity of substituents attached to ring atoms are available. The desilylation of the 1,3,4-thia-diazolium salt 124 by CsF gave the unstable 1,3-dipole 125 which was trapped with N-substituted maleimides to afford exclusively the < . 

A value for the polymerization enthalpy of 21.5 kcal/mole can be used to estimate percent conversion and rates for N-substituted maleimide/vinyl ether and maleic anhydride/vinyl ether copolymerizations. A value of 18.6 kcal/mole can be used for the enthalpy of polymerization of acrylate monomers to convert heat evolution data to percent conversion. Since the molar heats of polymerization for N-substituted maleimide vinyl ether copolymerization and acrylates vary by less than 20 percent, the exotherm data in the text are compared directly. 

The broad applicability of ATRP in the ionic liquid [BMIMjPFg was shown by extending it to the polymerization of N-substituted maleimides with styrene. The ATRP was initiated with dendritic polyaryl ether 2-bromoisobutyrate as the initiator at room temperature. The dendritic-linear block copolymers formed in the ionic liquid were characterized by low polydispersity (1.05chain-extension polymerization, suggesting the living nature of the polymerization 247). 

Heating of 1,2,3-triazolium-l-aminide 168 with acrylonitrile in dry acetone at reflux yielded a mixture of pyrrolo[2,3-similar reactions with different N-substituted maleimides produced only one product in each case. Table 6 summarizes the results of these reactions <2001J(P1)1778>. 

Among photooxidation products of the betaines 86 (R = Me, PhCH2, Ph, = H) are N-substituted maleimides (107). Evidence for the intermediate 108 in these reactions is provided by the observation that photooxidation of l-methyl-5-phenylpyridinium-3-olate (86 R = Me, R = Ph) gives the peroxy dimer 109 (11%). ... 

Recently, an antibody has been described which catalyzes not just a Diels-Alder reaction between an N-substituted maleimide and acetoxybutadiene (kcat = 0.055 s-1, Km = S3 mM, kcat/fCM = 6.6 (m s) but also the subsequent hydrolysis oftheacetoxy group (kcat = 9.2 x 1(T4 s 1, JCM = 1.1 rmvr, kcat/KM = 0.9 (m s) 1), which is about 1.5% as fast as the Diels-Alder reaction itself (Figure 18.9). 

Kalgutkar, A. S. Crews, B. C. Mamett, L. J. Design, synthesis, and biochemical evaluation of N-substituted maleimides as inhibitors of prostaglandin endoperoxide synthase. /. Med. Chem. 1996, 39, 1692-1703. 

A series of compounds of the type 120 was prepared by the condensation of ai-ferrocenyl aliphatic acids with aromatic o-diamines.115 The Diels-Alder reaction of 121 (R = H or CH3) with various N-substituted maleimides gave a series of compounds of the type 122.116 Only the endo isomers were formed. A number of additional nitrogen-... 

The t-BOC protected copolymers were prepared both by copolymerization of the t-BOC protected hydroxyphenylmaleimide monomer with styrene and by modification of preformed phenolic copolymers of various molecular weights as shown in Scheme I. In both cases the copolymer compositions were foxmd to be 1 1 based on NMR results and elemental analyses. The NMR and IR spectra obtained from copolymers from both routes were identical. The 13C and IH NMR spectra of the modified polymer are shown in Figures 1 and 2. These data substantiate the completeness of the protection reaction of the preformed phenolic copolymer. The copolymers are presumed to be predominately alternating since these comonomers represent an example of the classic general alternating copolymerization case of an electron rich comonomer (styrene) and an electron poor comonomer (N-substituted maleimide) (13). 

The generation of the carbcxi-carbon double bond of unsaturated nitrogen heterocycles by the rDA reaction of cycloadducts that act as protected ethylenes has been accomplished. Azetines have been prepared by this method. Another example is the synthesis of l-methyl-3-pyrroline (201). By protecting the ethylene of N-methylmaleimide (199) with furan and then reducing with lithium aluminum hydride, adduct (200) was obtained (equation 86). Pyrolysis of adduct (200) at 250-300 C gave l-methyl-3-pyrroline (201) in 60% isolated yield. The ethylene moiety of N-substituted maleimides can also be generated via rDA reactions. Examples include the generation of N-phenylmaleimide (equation 87) and of N-acetoxymaleimide (equation 88). ... 

The major gaseous degradation product of poly(N-substituted maleimides) is CO [12]. Two pathways are possible for the degradation of poly(N-arylmaleimides) with the formation of CO2. One is the imide-isoimide rearrangement followed by the elimination of CO2 as shown below ... 

In 1960, Natta reported the first direct synthesis of an optically active polymer from an achiral monomer, where methyl sorbate was polymerized using (R)-2-pentyllithium [95]. Ozonolysis of the polymer (under conditions possibly allowing epimerization) produced (S)-methyl succinic acid in 5% ee, which provides evidence of asymmetric induction and absolute configuration of the polymer main chain. Since this initial report, a remarkable void in the Hterature exists concerning the synthesis of main-chain chiral polymers from achiral monomers using anionic initiators. Okamoto and Oishi have polymerized N-substituted maleimides with chiral anionic initiators (Scheme 14) [96,97]. The polymer is assumed to have predominantly a frans-diisotactic microstructuxe, which adopts a secondary helical structure. The absolute configuration of the main chain has... 

Maleimide and N-substituted maleimides undergo photoaddition to benzene and alkylbenzenes to form 2 1 adducts Intermediate in the reaction is homoannular diene (formed by initial 2+2 cycloaddition) which subsequently undergoes 2+4 (Diels-Alder) cycloaddition to give diimide (Reaction 1). 

A number of (2 + 2)-cycloadditions of N-substituted maleimides with enamines occurred at 80° the reaction products (7) were formed in 40-90% yield.37 Similarly, 4-phenyl-4//-l,2,4-triazole-3,5-dione entered into a (2 + 2)-cycloaddition reaction via its electron-deficient nitrogen-nitrogen double bond. The reaction with enamines to give 8,37 or with 1,4-dioxene to give 9,38 took place at —60°. With less electron-rich olefins, such as indene38 or frans-2,3-dimethylmethylenecyclopropane,39... 

Annulation of heterocycles with a cyclobutene ring has been achieved by photochemical (2 + 2)-cycloaddition with acetylenes. Both maleic anhydride and N-substituted maleimides yielded 3-oxa- or 3-aza-bicyclo[3.2.0l-hept-6-ene-2,4-diones (167).,89,9° Vinylene carbonates also entered into a cycloaddition reaction with acetylenes to afford 168, which has been employed as starting material for the synthesis of cyclo-butadiene(tricarbonyl)iron or cyclobutenedione.19,-193 3,4-Dihydro-2/f-pyran and 5-methyl-2,3-dihydrofuran reacted with diphenylacetylene to... 

Pyridinium toluene-p-sulphonylmethylide (62), generated in situ from the pyridinium salt (61), serves as an equivalent of formyl anion, and, in the presence of an alcohol, it undergoes 1,4-addition to N-substituted maleimides to give (alkoxymethylene)succinimides (63). The protected aldehyde is liberated by treatment with hydrobromic acid (Scheme 26). ... 

Reaction of Amino Acids and Amines with N-Substituted Maleimides... 

Sharpless and Flavin (1966) have described the isolation and determination of the structures of the products arising from the reaction of certain primary and secondary amines and amino acids with N-substituted maleimides. Examples of the spectral properties are given in Table 9.2. 

Otsu, T., Motsumoto, T., Kubota, T., and Mori, S. 1990. Reactivity in radical polymerization of N-substituted maleimides and thermal stability of the resulting polymers. Polym. Bull. 23 43-50. 

One method of producing PVC copolymers with higher heat distortion temperatures than a comparable PVC homopolymer is to employ n-substituted maleimides as comonomers. The bulkiness introduced by the ring structure is beUevedto result in the improved heat distortion temperature (81). 

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