Imides reactions

Photosensitive functions are in many cases also heat sensitive, so the preparation of photosensitive polyimides needs smooth conditions for the condensations and imidization reactions. Some chemical reactants, which can be used for polyamide preparation, have been patented for the synthesis of polyimides and polyimide precursors. For example, chemical imidization takes place at room temperature by using phosphonic derivative of a thiabenzothiazoline.102 A mixture of N -hydroxybenzotriazole and dicyclohexylcarbodiimide allows the room temperature condensation of diacid di(photosensitive) ester with a diamine.103 Dimethyl-2-chloro-imidazolinium chloride (Fig. 5.25) has been patented for the cyclization of a maleamic acid in toluene at 90°C.104 The chemistry of imidazolide has been recently investigated for the synthesis of polyimide precursor.105 As shown in Fig. 5.26, a secondary amine reacts with a dianhydride giving meta- and para-diamide diacid. The carbonyldiimidazole... 

Most proteins contain an abundance of carboxylic acid groups from C-terminal functionalities and aspartic and glutamic acid side chains. These groups are readily modified with bis-hydrazide compounds to yield useful hydrazide-activated derivatives. Both carbohydrazide and adipic acid dihydrazide have been employed in forming these modifications using the carbodi-imide reaction (Wilchek and Bayer, 1987). 

The Derivative, 5-(biotinamido)pentylamine, contains a 5-carbon cadaverine spacer group attached to the valeric acid side chain of biotin (Thermo Fisher). The compound can be used in a carbodi-imide reaction process to label carboxylate groups in proteins and other molecules, forming amide bond linkages (Chapter 3, Section 1). However, the main use of this biotinylation reagent is in the determination of factor XHIa or transglutaminase enzymes in plasma, cell, or tissue extracts. 

Fig. 3.2 First-order kinetic plots for microwave (MW) and thermal (A) activation of the imidization reaction.

Sulfonamide derivatives of a-amino acids and the similar bissulfonamide derivatives of diamines can be used to prepare reactive Lewis acid complexes. Corey20 reported the Lewis acid (R,R)- or (5,5 )-complex 69, which can be employed at 10 mol% level to catalyze the Diels-Alder reaction of cyclopentadiene and imide. Reactions catalyzed by this complex give an endo.exo ratio of over 50 1, as well as a high ee (91%) at —78°C, and this can be further improved to 95% by carrying out the reaction at 90°C.20 The related aluminum complex 69b shows very similar reactivity at —78°C, with generally higher ee values, typically over 95%, for the reaction of cyclopentadiene derivatives with imide.20,21... 

The authors [1] studied kinetics of poly (amic acid) (PAA) solid-state imidization both in the presence of nanofiller (layered silicate Na+-montmorillonite) and without it. It was found, that temperature imidization 1] raising in range 423-523 K and nanofiller contents Wc increase in range 0-7 phr result to essential imidization kinetics changes expressed by two aspects by essential increase of reaction rate (reaction rate constant of first order k increases about on two order) and by raising of conversion (imidization) limiting degree Q im from about 0,25 for imidization reaction without filler at 7 i=423 K up to 1,0 at Na -montmorillonite content 7... 

In figure 1 the dependence pA(t) in double logarithmic coordinates, corresponding to the relationship (2), for solid state imidization reaction without filler at the four mentioned above imidization temperatures 7) are shown. As can be seen, the received dependences are linear and according to their slope the value ds can be obtained. The 7) increase in the range 423-523... 

As the results in Fig. IV show that cyclization proceeds at a very slow rate at 135°C but quite rapidly at 180 C, the log of concentration of polyamic acid vs time gives two straight lines which intercept at 90% conversion Fig. V. This can be interpreted to mean that imidization reactions can be divided into rapid and slow, first-order ring closure steps. These results are in general agreement with that reported by Kruez (8). 

Initial investigations of base-catalyzed imidization of polymeric systems, in particular PMDA/ODA based polyfamic alkyl esters), have been difficult due to the insolubility of the polyimide precursor at imidization levels exceeding 40%. Nevertheless, preliminary studies indicate that the base-catalyzed polymer imidization reaction appears to be significantly slower at ambient temperatures as compared to the phthalamide model compounds. It is yet unclear whether this is a direct result of the conformational aspects associated with the polymer chain or solubility considerations arising from the less soluble, partially imidized polymer chain. Since much of the initial work involved IR studies of supported... 

The PMR-15 chemistry looks very straightforward and ideal for the application as a composite matrix resin. In addition, the starting monomers are readily available and cheap. The fact that the imidization reaction, which forms the prepolymer at moderately low temperatures, could be separated from the crosslinking reaction was thought to be the key to easy laminate processing and void free laminates. However, after more than twenty years of research and development, it is known that both reactions are very complex and dependent... 

The rate is slower in basic aprotic amide solvents, and faster in acidic solvents such as / -cresol. In general, the imidization reaction has been shown to be catalyzed by acid (14,32,33). Thermal imidization of poly(amic acid)s is catalyzed by tertiary amines (34). High temperature solution polymerization in -cresol is often performed in the presence of high boiling tertiary amines such as quinoline as catalyst. Dialkylaminopyridines and other tertiary amines are effective catalysts in neutral solvents such as dichlorobenzene (35). Alkali metal and zinc salts of carboxylic acids (36) and salts of certain organophosphorus compounds (37) are also very efficient catalysts in one-step polycondensation of polyimides. 

Lewis, D.A., Summers, J.S., Ward, T.C. and McGrath, J.E., Accelerated imidization reactions using microwave radiation, /. Polym. Sci., Part A Polym. Chem., 1992, 30, 1647. 

Enantioselective conversions of aryl benzyl selenides to N-tosylselenimides 28 with [(tosylimino)iodo]benzene, cuprous triflate, and the chiral bis(oxazo-line) 22 have recently been demonstrated (Scheme 16) [37,38]. Because benzyl phenyl selenide undergoes uncatalyzed imidation with Phi = NTs in acetonitrile (46 % yield) or dichloromethane (trace yield), toluene was selected as the solvent for the asymmetric imidation reactions. Furthermore, in order to avoid racem-ization of 28 by moisture, molecular sieves were added to the reaction medium. 

We have recently patented the preparation of optically active thalidomide (1) by the imidation reaction of aminopiperidinedione with phthalic anhydride (4) in the presence of hexamethyldisilazane and ZnCh without racem-ization (Scheme 23) [100]. The process gives the thalidomide (1) in a reduced number of steps in a simple procedure and thereby is advantageous for industrial production of optically active thalidomide (1). Thus, a solution of 100 mg (S)-2-aminoglutarimide hydrobromide (46) in 5 mL benzene was treated with 92.0 mg phthalic anhydride (4), stirred for 1 h, treated with 98.0 mg ZnCl2 and 0.304 mL hexamethyldisilazane (HMDS), refluxed at 80 °C for 6 h, and cooled to room temperature. After the usual workup, (S)-thalidomide (1) was obtained in 58% yield with > 99% ee. (ft)-Thalidomide (1) can be prepared in the same way from (it)-47 with 99% ee in good yield. 

Whereas the proton transfer does not effect the stochiometry of the final PI when water is eliminated in the imidization reaction (fig. 3F), addition of an excess ODA molecule to polyamic acid could lead to the imine type crosslink formation schematically shown in figure 3G. This would lead to a deficiency of carbonyl oxygen atoms for vapor deposited polyimide and is consistent with our analysis. Mack et al. [16] proposed imine crosslink formation from their Raman spectroscopic studies for vapor deposited polyimides with excess ODA. In accordance with this model we attribute the low binding energy shoulder in the polyimide Nls line (figure 4c) to double bonded nitrogen species. However, the model gives no explanation for the carbonyl deficiency found in spin deposited polyamic acid and polyimide. In this case no excess of ODA is observed and only a very weak shoulder has been reported for the Nls line [4,11]. 

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