Imidic ester

Amidines are best made in two stages a nitrile reacts with dry HCl and anhydrous alcohols to give an imidic ester (imino-ether) which yields an amidine with NH3. 

The scheme below shows how the eastern and western parts of a corrin chromo-phore can be combined regioselectively. The western part has a more acidic enamine than the eastern part, whereas the imidic ester of the eastern part is more electrophilic. 

Polymers based on trimellitic anhydride are widely used in premium electromagnetic wire enamels requiring high temperature performance. Several types of trimellitic anhydride-derived polymers are used as wire enamels poly(amide—imide)s (133), poly(ester—imide)s (134), and poly(amide—imide— ester)s (135). Excellent performance characteristics are imparted by trimellitic anhydride-based polymers for wire enamel requirements of flexibiUty, snap, burnout, scrap resistance, heat shock, and dielectric strength. 

Reactions. Although carbapenems are extremely sensitive to many reaction conditions, a wide variety of chemical modifications have been carried out. Many derivatives of the amino, hydroxy, and carboxy group of thienamycin (2) have been prepared primarily to study stmcture—activity relationships (24). The most interesting class of A/-derivatives are the amidines which are usually obtained in good yield by reaction of thienamycin with an imidate ester at pH 8.3. Introduction of this basic but less nucleophilic moiety maintains or improves the potency of the natural material while greatiy increasing the chemical stabiUty. Thus /V-formimidoyl thienamycin [64221-86-9] (MK 0787) (18), C 2H yN204S, (25) was chosen for clinical evaluation and... 

Appllca.tlons. MCA is used for the resolution of many classes of chiral dmgs. Polar compounds such as amines, amides, imides, esters, and ketones can be resolved (34). A phenyl or a cycloalkyl group near the chiral center seems to improve chiral selectivity. Nonpolar racemates have also been resolved, but charged or dissociating compounds are not retained on MCA. Mobile phases used with MCA columns include ethanol and methanol. 

Peracid Precursor Systems. Compounds that can form peracids by perhydrolysis are almost exclusively amide, imides, esters, or anhydrides (85). Two compounds were commercially used for laundry bleaching as of 1990. Tetraacetylethylenediarnine (TAED) [10543-57-4] is utilized in over 50% of Western European detergents (5). The perhydrolysis reaction of this compound is shown in equation 19. T A ED generates two moles of peracid and one mole of diacetylethylenediamine per mole of imide (93). 

Als vinyloger Carbonsaure-imid-ester wird l-Athoxy-3-benzylimino-cyclohexen mit Natriumboranat oder Lithiumalanat unter 1,4-Addition in 80%iger Ausbeute ausschlieB-lich zu 1 -Athoxy-3-benzylimino-cyclohexan reduziert4 ... 

Monosubstituierte Carbamidsaureester lassen sich dagegen in 1,4-Dioxan durch Na-trium-acetoxy-trihydrido-borat in Ausbeuten von 65-80% d.Th. zu den entspre-chenden sekundaren Aminen reduzieren (s. S. 240)7. Die Reduktion mit Natriumboranat in Athanol ist dagegen iiber die entsprechenden Kohlensaure-imid-ester-Tetrafluorobo-rate moglich (s.S. 350f.)8. 

Carbonsaure-imid-ester Oder deren Salze werden durch Natriumboranat in neutralem Medium zu 0,N-Acetalen (s. S. 436 f.) (bzw. Aldehyden) Oder Aminen reduziert. Amidine und Imid-chloride gehen in Amine iiber, Formazane in Amid-hydrazone. 

Wie auf S. 347 erwahnt, konnen Carbonsaure-imid-ester mit Natriumboranat auch zu Aminen reduziert werden. Wird von Nitrilen ausgegangen, so werden sek. Amine erhalten3 4 ... 

The corresponding half-imidic esters have also been used to afford 3-amino-2(17/)-quinoxalinones. The following examples illustrate typical conditions and yields. 

Certain 1,3,4-oxadiazole and 1,2,4-triazole glyphosate derivatives have been conveniently prepared in a faster, more efficient manner by heating the thionoester intermediates 73 with the appropriate acid hydrazide (61). These versatile thionoesters 73 have been synthesized in nearly quantitative yield from the readily available nitrile 31a, described previously, through the intermediate imidate ester 72. The oxadiazole products such as 70 obtained using this procedure were identical to those obtained from the HHT approach. 

The t-butoxycarbonyl (rBoc) group is another valuable amino-protecting group. The removal in this case is done with an acid such as trifluoroacetic acid or /Moluenesulfonic acid.218 r-Butoxycarbonyl groups are introduced by reaction of amines with f-butoxypyrocarbonate or a mixed carbonate-imidate ester known as BOC-ON. 219... 

O-Allyl imidate esters undergo [3,3]-sigmatropic rearrangements to /V-allyl amides. Trichloromethyl imidates can be made easily from allylic alcohols by reaction with trichloroacetonitrile. The rearrangement then provides trichloroacetamides of IV-allylamines.260... 

Imidate esters can also be generated by reaction of imidoyl chlorides and allylic alcohols. The lithium anions of these imidates, prepared using lithium diethylamide, rearrange at around 0°C. When a chiral amine is used, this reaction can give rise to enantioselective formation of 7, 8-unsaturated amides. Good results were obtained with a chiral binaphthylamine.265 The methoxy substituent is believed to play a role as a Li+ ligand in the reactive enolate. 

Like oxalic acid, oxalic esters and o-phenyldiamines give 2,3(l/7,4/7)-quinox-alinediones that bear substituents according to those on the substrate such condensations appear to be assisted substantially by microwave irradiation.1036 The corresponding half-imidic esters have also been used to afford 3-amino-2(l/7)-quinoxalinones. The following examples illustrate typical conditions and yields. 

Cuatrecasas, P., and Parikh, I. (1972) Adsorbents for affinity chromatography. Use of N-hydroxysuccin-imide esters of agarose. Biochemistry 11, 2291-2299. 

Cyclic imidate esters, 2-ethoxypyrrolin-5-one and 2-ethoxy-1II -indol-3-one, undergo 1,3-dipolar cycloaddition reactions with nitrile oxides, the reaction site being at the pyrroline C=N bond (317). Rigid and sterically congested pyrroline spiro compounds 148 demonstrate complete diastereofacial selection in site and regiospecific cycloaddition reactions with nitrile oxides to give products 149 (318). 

AR Mitchell, SBH Kent, IC Chu, RB Merrifield. Quantitative determination of d-and L-amino acids by reaction with ferf-butoxycarbonyl-L-leucine A-hydroxysuccin-imide ester and chomatographic separation as d,l and l,l dipeptides. Anal Chern 50, 637, 1978. 

Free-radical cyclization on to unsaturated CN bonds and also the cyclization of a range of nitrogen-centred radicals have continued to attract interest and have been reviewed. Aryl radicals, generated from BusSnH- or TTMSS-mediated homolytic cleavage of aryl-bromide bonds, have been shown to cyclize on to the nitrogen atom of imidate esters in the 5-exo mode (Scheme 9). Loss of an ethyl radical leads to the observed A-acylindolines. No cyclization in the 6-endo mode was detected. 

A series of imidate esters derived from secondary alcohols has been found to react with potassium benzoate or potassium phthalimide to give products of 5 n2 substitution in excellent yields and with clean inversion of stereochemistry. ... 

Seelinger W, Aufderhaar E, Diepers W et al. (1966) Recent synthesis and reactions of cyclic imidic esters. Angew Chem 20 913-927... 

An example of the application of NOE difference spectroscopy is the configurational assignment of imidate esters 1. The E- and Z-isomers undergo rapid isomerization at room temperature, however, at — 58 °C the H-NMR signals of the diastereomers can be resolved303. 

Alternatively, the imide-acid chloride is reacted with methanol to give the imide ester which, after borohydride reduction and triethylsilane/trifluoroacetic acid treatment, furnishes the bicyclic lactam 6 as a racemate. The latter is acylated with either propanoyl chloride or 3-phcnylpropanoyl chloride and the resulting amides 7 deprotonated and alkylated with (bro-momethyljbenzene or iodomethane, respectively, to give the major alkylation products 8 with d.r. >98 2 and in 65% yield3. 

L. E, Overman, Acc. Chem. Res. 13, 218-223 (1980 Allylic and Propargylic Imidic Esters in Organic Synthesis". 

Pretzer et al. (4) prepared high-performance resins consisting of trimellitic anhydride imide esters derived from ethanol amine, ethylene glycol, and pyromellitic dianhydride that were used in applications requiring good mechanical properties and heat and fire resistance. 

Laser irradiation of isatin (70) gave 71 as a result of bimolecular condensation (78TL3007). The diazine ring of 73 was formed during the cyclocondensation of anthranilic acids with the imidate esters derived from indolinone (72) (81AP271). 

Synthesis of the pyrazino[2,1 -bjquinazoline (557) was achieved by oxidative cyclization of the l-(2-aminobenzyl)-4-methylpiperazine (556) with manganese dioxide [68JCS(C)1722], the pyrimidine ring of 557 was formed during this synthesis. The pyrimidine ring of 559 was also formed upon cyclocondensation of anthranilic acids with the cyclic imidate ester (558), followed by removal of the protective group (66USP3280117). 

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