Methylpyrrole-2-Carboxylic Acid

Apparatus For the metallation Chap. I, Fig. 1, 500 ml. For the carboxylation 1-1 round-bottomed flask, equipped with a gas-inlet tube, a mechanical stirrer and a rubber stopper with a hole of 5 mm diameter. For the addition of the solution of the lithiated pyrrole 50 to 100 ml syringe. 

For carboxylations with carbon dioxide reversed-order addition is generally carried out, i.e. the solution or suspension of the metallated compound is poured on the powdered dry ice , which may be covered with an organic solvent. The reason for applying this technique is that alkali salts of carboxylic acids can undergo an attack by the organometallic derivative  

Reversed-order addition is also applied in the alternative procedure for 1-methyl-pyrrole-2-carboxylic acid. In this way the chance of introduction of moisture is minimized. This method is generally applicable if the organometallic intermediate is 

The metallation of 1-methylpyrrole proceeds considerably less easily than that of thiophene and furan. With the butyllithium TMEDA complex in hexane, however, this pyrrole derivative can be lithiated in a short time. Since THF is attacked very readily by BuLi TMEDA, it cannot be used as a co-solvent during the metallation. It is added when the metallation in hexane is complete. 

1-Methylpyrrole is used in excess to be sure that no butyllithium is present during the reaction with C02 the pentanoie acid formed from BuLi might give rise to difficulties in the purification of the pyrrole carboxylic acid. 

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Figure 3. Cyclic voltammograms of 3-methylpyrrole-4-carboxylic acid in acetonitrile + 0.1 MEt4NC104.58 (Reprinted from P. G. Pickup, Poly-(3-methylpyrrole-4-carbox-ylic acid) An electronically conducting ion-exchange polymer, J. Electroanal. Chem. 225, 273-280, 1987, with kind permission from Elsevier Sciences S.A.)...

Figure 5.24 Cyclic voltammetry of poly(3-methylpyrrole-4-carboxylic acid) films as a function of pH. (Reprinted from Journal of Electroanalytical Chemistry, 225, P. G. Pickup, 273. Copyright (1987), with permission from Elsevier.)...

The behavior of poly(3-methylpyrrole-4-carboxylic acid) was not clearly identified as self-doping since the focus was on the electrostatic binding of cations such as [Co(bpy)3] and methyl viologen, MV +. 

Example 8 Polypyrrole-Carboxyl Add - Electrochemical Synthesis of Poly(3-methylpyrrole-4-carboxylic Acid)... 

Figure 20.40. Stmcture of poly(3-methylpyrrole-4-carboxylic acid).

Following the discovery of the unique electronic properties of polypyrrole, numerous polymers of pyrrole have been crafted. A copolymer of pyrrole and pyrrole-3-carboxylic acid is used in a glucose biosensor, and a copolymer of pyrrole and A-methylpyrrole operates as a redox switching device. Self-doping, low-band gap, and photorefractive pyrrole polymers have been synthesized, and some examples are illustrated [1,5]. 

Scheme 6.92 Generation of the cephalosporin-derived cyclic allene 450 from the cephalosporin / -S-oxide triflate 449 and trapping of450 by (Z)-/J-deuterostyrene, furan, 2-acetylfuran, furan-3-carboxylic acid dimethylamide, N-tert-butoxycarbonylpyrrole, pyrrole and N-methylpyrrole.

The condensation of amino sugars with /3-keto esters in an alkaline medium results in considerable degradation of the (tetrahydroxybu-tyl)pyrrole produced, giving rise to small yields of 2-methylpyr-role,57,58 which seems to be the main chromophore in the Elson-Morgan reaction. Under these conditions, 3-amino-3-deoxyhexoses yield 2-methylpyrrole-4-carboxylic acid,59 which is, in part, responsible for the coloration produced with p-(dimethylamino)benzaldehyde. 

Oxidation of 2-methylpyrrole under more vigorous conditions with potassium permanganate or chromic acid produces pyrrole-2-carboxylic acids or maleimides (see Section 3.05.1.4). 

Scheme 2 Synthesis of 4-(fert-Butoxycarbonylamino)-l-methylpyrrole-2-carboxylic Acid A Heterocyclic Subunit for Several Naturally Occurring Oligopeptidesl101...

C6H7N02 N-methylpyrrole-2-carboxylic acid 6973-60-0 453.15 39.402 2 7349 C6H8N20 2-methoxy-3-methylpyrazine 2847-30-5 579.00 51.524 2... 

To the first class belong those analogues which, unmodified in the side chain, contain a different number of residues of 4-amino-l-methylpyrrole-2-carboxylic, acid. In the second class are considered those analogues which show modifications in side chains of the distamycin molecule. These modifications have been achieved either in the propionamidine side chain, or in the formyl-amino side chain. These analogues have been synthesized by Arcamone et a .25, 26). 

Ludwig. This compound has an empirical formula corresponding to structure (1) and shows the ultraviolet and infrared" absorptions of a pyrrole-3-carboxylic ester. Its acetylation gives a tetra-O-acetyl derivative." Oxidation with lead tetraacetate yields ethyl 5-formyl-2-methyl-pyrrole-3-carboxylate (4), identical with the compound prepared in a different way. Oxidation with potassium permanganate in alkaline solution at low temperature yields 3-(ethoxycarbonyl)-2-methylpyrrole-5-carboxylic acid (7) which can be transformed " into the diethyl ester (8), identical... 

Ethyl 2-methyl-4-(D-ara6mo-tetrahydroxybutyl)pyrrole-3-carbothiolate (18) yields a tetra-O-acetyl derivative, and, on oxidation with periodic acid, affords ethyl 4-formyl-2-methylpyrrole-3-carbothiolate (22). Lactone (27) gives a tri-O-acetyl derivative and, on alkaline hydrolysis, consumes one equivalent of base and furnishes 2-methyl-4-(D-arofemo-tetrahydroxy-butyl)pyrrole-3-carboxylic acid (19) in almost quantitative yield. This acid can, in turn, be transformed into a tetra-O-acetyl derivative, and, when oxidized with sodium metaperiodate, it gives 4-formyl-2-methyl-pyrrole-3-carboxylic acid (23). Attempts to determine the size of the lactone ring in compound (27) by oxidation with sodium metaperiodate were unsuccessful three moles of metaperiodate were consumed per mole, as if, during the oxidation, hydrolysis of the lactone had occurred. 

The reaction of l-amino-l-deoxy-n-fructose with 2,4-pentanedione gives 3-acetyl-2-methyl-4-(D-araZ)mo-tetrahydroxybutyl)pyrrole (20). Acetylation of this compound yields a tetra-O-acetyl derivative, and periodate oxidation of (20) furnishes 4-acetyl-5-methylpyrrole-3-carboxaldehyde (24), which can be subsequently oxidized to 4-acetyl-5-methylpyrrole-3-carboxylic acid (26). 

The methyl ester of l-methylpyrrole-2-carboxylic acid can be prepared in a similar way from 2-lithio-l-methylpyrrole (prepared as described in Exp. 8) and CICOOCH3. The boiling point of the ester is ca. 50 °C/0.5 mm, n 2 1.5132, the yield is 65 %. 

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