2.3- dicarboxy-, preparation

This dicarboxy-terminated oligomer is prepared by reacting excess adipic acid with 1,2-edianediol in die bulk until hydroxyl group conversion is complete (Scheme 2.47). The molar mass of final polymer depends on the initial molar ratio of monomers (procedure similar to that described in ref. 401). 

Scheme 3 shows the details of the synthetic strategy adopted for the preparation of heteroleptic cis- and trans-complexes. Reaction of dichloro(p-cymene)ruthenium(II) dimer in ethanol solution at reflux temperature with 4,4,-dicarboxy-2.2 -bipyridine (L) resulted the pure mononuclear complex [Ru(cymene)ClL]Cl. In this step, the coordination of substituted bipyridine ligand to the ruthenium center takes place with cleavage of the doubly chloride-bridged structure of the dimeric starting material. The presence of three pyridine proton environments in the NMR spectrum is consistent with the symmetry seen in the solid-state crystal structure (Figure 24). 

HPMA [36] and a vinyl metal-chelating monomer A-(A/, A/ -dicarboxy-methylaminopropyl)methacrylamide synthesized [35]. Chemical structures of HPMA and DAMA are given in Figure 4. Poly(HPMA-co-DAMA) was prepared by free radical copolymerization in methanol with AIBN as initiator. Molecular weight distribution was determined by size exclusion chromatography and content of side-chain carboxylic group by acid-base titration. 

Bose et al. [74] have investigated the novel synthetic route for the preparation of spirobarbiturates-a class of compounds known for their interesting physiological activity. The synthesis of spiro-fi-lactams 3 (Scheme 1) was achieved by the reaction of 4,4-dicarboxy-/V-phenylazetidin-2-one 1 with carbodiimides 2 in tetra-hydrofuran. 

Scheme 1 Preparation of spirobarbiturates using 4,4-dicarboxy-/V-phenylazetidin-2-one and carbodiimides...

Water-soluble poly(p-phenylene) 24, shown in Scheme 29, was prepared by the introduction of carboxylic acid pendant substituents along the p-phenylene chains [102]. In initial work in this area, a dicarboxy-substituted dibromobiphe-nyl was polymerized with 4,4f-biphenyl bis-boronic acid via Suzuki coupling... 

Besemer, A.C., Jetten, J.M., and van Bekkum, H., A novel procedure for the preparation of dicarboxy-inulin, in Fifth Seminar on Inulin, Fuchs, A., Ed., Carbohydrate Research Foundation, The Hague, 1995, pp. 25-34. 

Amino-2-carboxyphenylarsinic acid is the reduction product of the preceding nitro-acid, using ferrous sulphate in alkaline solution. It is an intermediate in the preparation of 2 2 -dicarboxy-4 4 -dihydroxyarsenobenzene, but is not isolated in the solid state (p. 855). 

Methylpyrazine. 2-Methylpyrazine has been prepared by decarboxylation of 2from glucose with 25% aqueous ammonia at 100° (33) by dehydrogenation of 2-methylpiperazine (or Mbutyl-2-methylpiperazine) over copper chromite at elevated temperatures (470, 471) (Section 11.6) and in high yield by dehydrogenation of methylpiperazine over catalysts containing CuO, Cr Os, or MnOi at 350-370° (469). Other catalysts have also been used for this dehydrogenation (471,562). 

Bredereck and Schmotzer (1044), from diaminomaleonitrile (DAMN hydrogen cyanide tetramer) and oxalyl chloride, prepared 2,3-dicyano-5,6-dihydroxy-pyrazine but Stetten and Fox (1049) could not prepare 23-diamino-5-hydroxy-pyrazine from glycine amide and oxamide. Section 11.3 lists preparations from a, -diamino or a, -diimino compounds and reagents other than a,0-dicarbonyl compounds (384) with additional data (1050) and oxidation of 23-dichloro-quinoxaline with hot aqueous potassium permanganate gave 23-dicarboxy-5,6-dihydroxypyrazine (1051). 

Dicarboxy-5,6-dimethylpyrazine, heated with acetic anhydride, also gave the anhydride which with methanol gave 2-carboxy-3-methoxycarbonyl-5,6-dimethylpyrazine (654). 2,3-Dicarboxy-5-methylpyrazine anhydride was prepared similarly and on methanolysis and decarboxylation it gave 2-methyl-5(and 6)-methoxycarbonylpyrazines (1327). 

Reduction of 2-carboxypyrazine in aqueous potassium hydroxide over palladium-charcoal at 50° and atmospheric pressure gave 2-carboxypiperazine and 2,3-dicarboxy-, 2,5-dicarboxy-, 2,6-dicarboxy-, and 2-carbamoyl-3-carboxy-piperazines were prepared in an analogous manner (1269). Similar results were obtained on reduction of the calcium salts (1352). Reduction of 2-chlorocarbonylpyrazine with lithium tri-r-butoxyaluminohydride in tetrahydrofuran gave 2-(pyrazin-2 -ylmethoxycarbonyOpyrazine (1077). 

Carbamoylpyrazine refluxed with acetic anhydride gave 2-)V-acetylcarbamoyl-pyrazine (138,1418) and 2,5-bis-A -acetylcarbamoylpyrazine was prepared similarly (672). 2,3-Dicarbamoylpyrazine heated in a vacuum gave the imide of 2,3-dicarboxy-pyrazine (397). 

Reduction of 2-carbamoylpyrazine in ethanol over palladium-charcoal at atmospheric pressure gave 2-carbamoylpiperazine (870, 1269, 1352), and the 2-carbamoyl-3-carboxy (1269) and 2,3-dicarbamoyl (1269, 1352) analogues were prepared similarly, but 2,3-dicarboxypyrazine imide gave 50% 2,3-dicarboxy-1,4,5,6-tetrahydropyrazine imide (1269). 2-Hydroxy-3-V-phenylcarbamoylpyrazine oxidized with hydrogen peroxide in acetic acid at 50° for 96 hours did not give an 7V-oxide but only a tar and 2,3-dihydroxypyrazine (1055). 

Anhydrides of cis-cyclopropane-1,2-dicarboxy lie acids are converted to CM-2-acylcyclo-propanecarboxylic acids using various reagents. The outcome of the reaction is sensitive to the reaction conditions. Treatment of c i-3-oxabicyclo[3.1.0]hexane-2,4-dione with phenylmag-nesium bromide at low temperature" and dimethylcadmium at room temperature gave c/s-2-benzoyl- and c -2-acetylcyclopropanecarboxylic acid in 53 and 70% yield, respectively in addition minor amounts of disubstituted lactones were formed. 1129,1251 jjowever, no lactone was formed when cis-2-benzoylcyclopropanecarboxylic acid was prepared in 66% yield by reacting c -3-oxabicyclo[3.1.0]hexane-2,4-dione with benzene under Friedel-Crafts conditions." ... 

Dicarboxy pyrroles were first reported in the literature many years ago (3). These compounds are prepared by the... 

The conditions for this reaction are the same as those used by earlier workers to prepare mono dicarboxy pyrrole derivatives (3-jJ). Upon cooling of the acetic acid reaction solution the product, bis pyrrole derivative, crystallizes out and is recovered in sufficient purity to be used without further purification. Attempts to hydrolyze the bis(dicar-boethoxy pyrrole) derivatives in aqueous NaOH proved unsuccessful due to the high degree of insolubility. 

At the same time an important paper (67) appeared in which essentially the same conclusions with regard to the structure of bebeerine were arrived at by a different route. Faltis, Kadiera, and Doblhammer (67) treated the inactive a, a -dimethylbebeerine methine, obtained by a one-stage Hofmann degradation of bebeerine dimethyl ether, with ozone and obtained a mixture of two dimethylamino dialdehydes. These were not isolated but were converted to the chloromethylate derivatives, oxidized with potassium permanganate to the acids, and boiled with dilute alkah to decompose the quaternary bases. Besides trimethylamine, a mixture of two vinyl carboxylic acids were obtained. One of these proved to be 4, 6-dicarboxy-2,3-dimethoxy-5-vinyldiphenyl ether (LIX). The other vinyl carboxylic acid, which was readily separated from LIX by virtue of its low solubility, was first decarboxylated by heating with quinoline and naturkupfer C and then oxidized with potassium permanganate in acetone. This yielded 4-carboxy-2,2 -dimethoxydiphenyl ether (LXIII), the structure of which was proved by direct comparison with the synthetic compound prepared by the Ullmann condensation of o-bromoanisole and vanillic acid. 

Two pathways for the preparation of 1,4-dihydropyridazine derivatives were envisaged. According to the first, dimethyl 3-oxopentane-l,5-dioate (dimethyl acetone-1,3-dicarboxylate) (1) was treated in ethanol and sodium acetate at 0 °C with acidic aqueous diazonium salts, prepared from aromatic or heteroaromatic amines, to give hydrazones 69 in 35-94% yields. They were next treated with DMFDMA in dichloromethane at room temperature to form the (dimethylamino) methylidene derivatives 70 as intermediates, which immediately cyclized into dimethyl 1 -(hetero)aryl-4-oxo-l, 4-dihydropyridazine-3,5-dicarboxy-lates 71 in 72-94% yields, except for 71 (R=lH-l,2,4-triazol-3-yl), which was obtained in 35% yield (08ZN(63b)407) (Scheme 23). 

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