Potassium salt of pyrrole

Ciamician and Dennstedt reacted the potassium salt of pyrrole with chloroform in ether and isolated, after much purification, 3-chloropyridine, which was confirmed by crystallization with platinum. While the pyrrole salt can be used as the base, the chloroform carbene is typically formed with an alkali alcohol. Forty years later, Robinson and co-workers made 3-chloroquinolines from indoles using the Ciamician-Dennstedt reaction. ... 

In the reaction of EMME and the potassium salt of pyrrole in tetrahydro-furan (THF) at 0°C for 30 min, an addition product, ethoxy(l-pyrrolyl)-methylmalonate (115), could be isolated in 85% yield (82CB714). This ester (115) was hydrolyzed with potassium hydroxide in aqueous ethanol at reflux temperature to yield 95% dipotassium ethoxy( 1 -pyrrolyI)methylene-malonate (116), from which 1-pyrrolylmethylenemalonic acid (118) was... 

Potassium salts of pyrrole, 2-acetylpyrrole, 1,2,3,4-tetrahydrocarbazole, 9-carbazole, indole, imidazole, and 1,2,4-triazole react with [Tr-CjHjFe ( 0)2 ] to form ct-N derivatives, e.g., [7r-C5H5Fe(CO)2(CT-N-pyrrolyl)] (III) (400, 421), shown to be intermediates in the formation of the n-complexes e.g., (IV) (400). Anions [M(CO)5L] (M = Cr, Mo, W) were similarly prepared from the hexacarbonyls and alkali metal derivatives of succinimide, phthalimidine, and saccharin (49). 

An enzymatic carboxylation was reported, in supercritical CO2 (see p. ), in which exposure of pyrrole to Bacillus megaterium PYR2910 and KHCO3 gave the potassium salt of pyrrole-2-carboxylic acid. ° ... 

The case of ethoxycarbonylation has also been mentioned (p. 66). Whilst potassium salts of pyrrole and alkyl pyrroles react with ethoxycarbonyl chloride to give l-ethoxycarbonylpyrroles257, 291-2 the lithium salts form... 

With electrophilic substitutions carried out in basic media, the possible role of the pyrrole anion has to be considered. Again, no evidence is available. In reactions carried out with sodium or potassium salts of pyrroles, the observed result might sometimes be ascribable to the pyrrole anion, but often... 

Irradiation of the potassium salt of the substituted cyclopenta[b]pyrrole-2-carboxylic acid 389 results in formation of the central piperazine core of 390 following decarboxylation (Equation 104) <20010L537, 2003JA10664>. 

Most of the polymer modifications incorporating benzo-substituted pyrroles have been done with the dibenzo derivative, carbazole, primarily because of its well-known photocon-ductive properties. The modification reaction often involves a substitution reaction on some halogenated polymer. This substitution reaction can be quite facile. Poly(vinylbenzyl chloride), for example, reacts with the potassium salt of carbazole in DMF to yield the carbazole-functional polymer in 97% yield (76MI11110). 

Examples of ( 7 -C4N) coordination in pyrrole-derived macrocyles may be found in the reaction products of uranium halides with the tetraanion of the macrocycle [(-CH2-)5]4-calix[4]tetrapyr-role. " " As described in Equation (30), the reaction of Ul3(THF)4 with the potassium salt of the tetrapyrrolide in THF generates a dinuclear complex, [ [(-CH2-)5]4-calix[4]tetrapyrrole -UK(THF)3]2(/4-0) 2THF the 0x0 group is proposed to come from deoxygenation of a THF molecule ... 

Substituted indoles are of biological interest and are not readily synthesized by conventional methods of indole chemistry. Annulation of a nuclear methyl and an a-ethoxyimine (or an imidate) under basic conditions is a promising procedure. The pyridine oxide ester (87.1) may be converted in high yields into two kinds of pyrrole carboxylic ester the potassium salt of the imidate, on heating in DMF, gives the 3-(2-oxocarboxylate) whereas dilute mineral acid leads to the 2-carboxylate ester. 

Heating the sodium salt of pyrrole-2-carboxylic acid with methyl iodide in a sealed tube at 120°C gave the first example of an isopyrrole, formulated9 as 1 or its isomer (2). The same compound, having a menthol- or camphor-like odor, was isolated together with a methylenepyrroline formulated as 3 on treatment of 2,3,4,5-tetramethylpyrrole with methyl iodide and potassium... 

Nicotyrine, C10H10N2, a base found in tobacco (384, 392, 385), is a colorless oil, b.p. 280-281°, 150°/15 mm., 1.124. It forms a dipicrate, m.p. 170-171°, a chloroplatinate, m.p. 160° (dec) and a methiodide, m.p. 211-213°. It had been prepared synthetically long before its occurrence in tobacco was discovered. 3, 2-Nicotyrine is an intermediate in Pictet s synthesis of Z-nicotine (365). The methylation of the potassium salt of nornicotyrine yields nicotyrine (366), which is 2-(3 -pyridyl)-iV-methyl-pyrrole. It is obtained as the product of the dehydrogenation of nicotine with silver oxide (330). The dehydrogenation of nicotine with sulfur in boiling toluene yields thiodinicotyrine and 2,5% of nicotyrine (386). Nicotine when passed over platinized asbestos at 320° yields a mixture of nicotyrine and dihydronicotyrine (387). 

Teixidor et al. [49] synthesized self-doped polypyrrole by using the nonconventional covalently bound low charge density anion [3,3 -Co(1,2-C2B9Hio)2] to a pyrrole unit via a spacer diether aliphatic chain. The electropolymerization of the potassium salt of the monomer, denoted as [1] , (Figure 5.7) was obtained in dry acetonitrile with tetrabutyl ammonium chloride in the potential range of —0.5 to 1.7V vs Ag/AgCl. Similarly a copolymer of [1] was prepared with pyrrole monomer (ratio 1 1) under identical conditions. The conductivity of poly[l] and copolymer films measured using a four-point probe... 

A mild and effective method for obtaining N- acyl- and N- alkyl-pyrroles and -indoles is to carry out these reactions under phase-transfer conditions (80JOC3172). For example, A-benzenesulfonylpyrrole is best prepared from pyrrole under phase-transfer conditions rather than by intermediate generation of the potassium salt (81TL4901). In this case the softer nature of the tetraalkylammonium cation facilitates reaction on nitrogen. The thallium salts of indoles prepared by reaction with thallium(I) ethoxide, a benzene-soluble liquid. 

The cydization can also be carried out on a-tosylaminoallenes, in which case the choice of reaction conditions determines whether the product is the N-tosyl-3-pyrro-line or whether elimination of toluenesulfonic acid acid gives the pyrrole. For example, in the presence of catalytic silver nitrate, allene 141 (Eq. 13.47) rearranges to N-tosylpyrroline 142 in excellent yield, whereas when 141 is treated with potassium tert-butoxide in DMSO, pyrrole 143 is formed in 71% yield [54]. Warming the lithium salt of 141 in DMSO also leads to 143. The rearrangement of 141 to 143 may be mechanistically related to the conversion of 130 to 131 (Eq. 13.42). 

As with the reaction of pyrroles, diazoles and triazoles react with propargyl bromide to yield TV-substituted products and, depending upon the base strength, either TV-prop-2-ynylazoles or allenic derivatives are formed [30]. Generally, with potassium carbonate under soliddiquid two-phase conditions at room temperature in the absence of a solvent, the prop-2-ynyl compounds are formed as sole products, whereas with solid potassium hydroxide at elevated temperatures the allenes are obtained as the major products. Benztriazole produces a mixture of the N1- and N2-prop-2-ynyl, and N2-allenic derivatives, whereas with potassium hydroxide only the N -allenic derivative is obtained. The alkynes readily isomerize to the allenes in the presence of base and the quaternary ammonium salt, or upon treatment with methanolic sodium hydroxide. A series of l-(alk-2-ynyl)imidazoles have been prepared, as intermediates in the synthesis of imidazopyridines [31 ] and the reaction of 3-hydroxymethylpyrazoles with propargyl bromide leads to pyrazolooxazines [32]. 

Pyrroles can be converted into alkali metal salts (with NaNH2/NH3 or K/toluene) (see also Section 2.3.3.1). The use of pyrrolyl or indolyl sodium or potassium salts under ionizing conditions favors the formation of A-acyl or IV-alkyl derivatives (Scheme 4) (740S(54)58,74OS(54)60). 

However, of all the salts tested (RbCl, CsF, CS2CO3 0.2 mol per 1 mol KOH), only cesium fluoride shows a perceptible catalytic effect (yield gain up to 8%) at the stage of pyrrole formation for only the first three hours (Fig. 2, curve 3). The observed effect can be explained in terms of poor solubility of potassium fluoride in DMSO (86MI1). 

Rubidium chloride even slows the reaction, this is especially well seen within a time span of 1-3 hr after the start of the process (Fig. 2, curve 2). In this case the normal salt effect is likely to prevail over the effect of oximate ion pair separation due to substitution of the potassium cation by the rubidium cation. The addition of cesium carbonate during the first 1.5 hr does not much affect the rate of the formation of 2-phenylpyrrole. The accelerating effect of these additives becomes evident only 2 hr after the beginning of the reaction and gradually increases (5 hr later the yield gain of pyrrole is 7% as compared with a standard run, Fig. 2, curve 4) which seems to result from a slow rate of heterophase exchange process ... 

The acidic character of cyclopentadienes forms an interesting example of a similar influence. This hydrocarbon remarkably enough readily forms a potassium salt. While for cyclopentadiene one configuration is mainly of interest (we thus neglect conjugation), the ion has quite the same electron system as pyrrole and, therefore, also the same very appreciable stabilization by resonance. 

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