Pyrrole-2-carboxylic acid esters, from

Pyrrole-2-carboxylic acid esters, from pyrrol-2-yl trichloromethyl ketone, 51, 102 PYRROLE—2-CARBOXYLIC ACID,... 

Potassium tert-butanol Pyrrole-2-carboxylic acid esters from tosylglycine esters via 3-hydroxypyrrolidine- and J -pyrroline-carboxylic acid esters... 

The most convenient laboratory method for the preparation of 2,4-dimethyl-5-carbethoxypyrrole is that given above. A cheaper method of obtaining large quantities consists in the partial hydrolysis of 2,4-dimethyl-3,5-dicarbethoxypyrrole with sulfuric acid, followed by decarboxylation. The ester has been obtained also by the alcoholysis of 5-trichloroaceto-2,4-dimethyl-pyrrole in the presence of sodium ethylate. The free acid has been obtained fronii-[2,4-dimethylpyrrole-5]-2,4-dimethylpyrrole-5-carboxylic acid and from 2,4-dimethylpyrrole-5-aldehyde. ... 

Pyrrole-2-carboxylic acid esters have been prepared from ethyl chloroformate and pyrrolylmagnesium bromide1 2 or pyrrolyllithium,3 by hydrolysis and decarboxylation of dimethyl pyrrole-1,2-dicarboxylate followed by re-esterification of the 2-acid4 and by oxidation of pyrrole-2-carboxaldehyde followed by esterification with diazomethane.4... 

Nearly 1000 compounds have so far been identified in the volatile constituents of meat from beef, chicken, mutton and pork (6). The largest number of volatiles has been determined in beef and these were representative of most classes of organic compounds. Hydrocarbons, alcohols, aldehydes, ketones, carboxylic acids, esters, lactones, ethers, sulfur and halogenated compounds as well as different classes of heterocyclic substances (Figure 1) namely furans, pyrldlnes, pyrazines, pyrroles, oxazol(in)es, thiazol(in)es, thiophenes were present in cooked meat flavor volatiles as shown in Table I. Many of these compounds are unimportant to the flavor of meat and some may have been artifacts (16). 

Diazabicyclo[ 5.4.0 Jundec- 7-ene Pyrroles from 1,1-nitroethylene derivs. PyrroIe-2-carboxylic acid esters... 

Grignard reagent from, acylation, 4, 237 nitration, 4, 211 reactivity, 4, 71-72 synthesis, 4, 149, 237, 341, 360 Pyrrole-3-carboxylic acids acidity, 4, 71 decarboxylation, 4, 286 esterification, 4, 287 esters... 

Yamanaka and co-workers (74) effected the 1,3-dipolar cycloaddition between miinchnones 134 and polyfluoro-2-alkynoic acid esters to afford the corresponding 4-(polyfluoroalkyl)pyrrole-3-carboxylates (135). The reaction proceeds rapidly at low temperature and the various miinchnones (134) were generated from 1,3-oxazolium perchlorates 133 using the method of Boyd and Wright (6,7). Under... 

Pyrrole- and indole-carboxylic acid chlorides react with dialkyl- and diaryl-cadmium to yield the ketones and it is noteworthy that the reaction of the anhydride of indole-2,3-dicarboxylic acid with diphenylcadmium produces 3-benzoylindole-2-carboxylic acid and not its isomer (53JCS1889). The ability of l-methylindole-2-carboxylic acid to react with nucleophiles is enhanced by conversion into the mixed anhydride with methanesulfonic acid. The mixed anhydride reacts with carbanions derived from diethyl malonate and from methyl acetate to yield the indolyl (3- keto esters (80TL1957). 

The 2H-and 3//-pyrroles and -indoles are considerably more basic than the corresponding H-isomers and they readily undergo alkylation to give the quaternary salts, which are then highly susceptible to nucleophilic attack. Thus, for example, methylation of the trialkyl-3//-indole (507), followed by reaction with aqueous base, yields the indolin-2-ol (508). A similar reaction sequence results from the acylation of (507) under Schotten-Baumann conditions to give (509 X = OH). When the benzoylation is conducted in benzene in the absence of the base, the 2-chloroindoline (509 X = C1) is formed and acylation of (507) with a carboxylic acid anhydride produces the ester (509 X = OCOR) (79HC(25-3)l). 

The carboxylic acid family of substituents is most often introduced at the stage of ring synthesis for both pyrroles and indoles. Many of the cyclizative condensation routes to pyrroles in fact rely on the presence of ester substituents. Indoles with 2-carboxy substituents are easily available from the adaptation of the Fisher synthesis, which provides the arylhy-... 

A new metabolite from Streptomyces olivaceus has been shown to be (2S)-1-oxo-2,3-dihydropyrrolizine-3-carboxylic acid (15b) by total synthesis. The pyrrolizine ring was formed from the pyrrole (14) by stereoselective cyclization with phosphorus pentoxide in toluene in 37% yield. Partial racemization occurred during the hydrolysis of ester 15a.21... 

Pyrrolo[2,1 -d][ 1,5]benzothiazepine-6-carboxylic acid (27) was obtained via base-catalyzed cyclization of pyrrole-2-carboxaldehydes 26 and 28, each synthesized by Vilsmeier-Haack formylation of their respective pyrroles 24 and 25, prepared in turn by condensation of 18, respectively, with ethyl bromoacetate and chloroacetonitrile in the presence of sodium ethylate at room temperature. When treated with piperidine in refluxing benzene for 48 hours, 26 and 28 afforded ester 29 and nitrile 31 from which, in an alkaline medium, acid 27 could be obtained. Under similar experimental conditions, acid 27 was also formed from amide 30 (Scheme... 

A comparison of the absorption and fluorescence properties of 3,5-diaryl-l//-pyrrole-2-carboxylic acid ethyl esters reveals marked effects of/i-dimethylamino and o-methyl substituents on the phenyl group at C-3 and suggests that in the presence of these substituents emission occurs either from a charge transfer state or from a combination of charge transfer and locally excited states <2005NJC1258>. 

Several new routes involve formation of one carbon-carbon bond in pre-formed substrates. Palladium-catalyzed cyclization of /3-hydroxyenamine derivatives has been employed in a route to substituted pyrroles and 4,5,6,7-tetrahy-droindoles with multiple substituents by formation of the C-3-C-4 bond as the key feature, as illustrated by construction of the molecule 534 (Equation 146) <2006T8533>. Zinc perchlorate-catalyzed addition of alcohols to the nitrile functionality of a-cyanomethyl-/3-ketoesters, followed by annulation gave access to a series of substituted ethyl 5-alkoxypyrrole-3-carboxylates <2007T461>. Similar chemistry has also been used for synthesis of a related set of pyrrole-3-phosphonates <2007T4156>. A study on preparation of 3,5,7-functionalized indoles by Heck cyclization of suitable A-allyl substituted 2-haloanilines has also appeared <2006S3467>. In addition, indole-3-acetic acid derivatives have been prepared by base induced annulation of 2-aminocinnamic acid esters (available for instance from 2-iodoani-lines) <2006OL4473>. 

Heterocyclic compounds containing a nitrogen atom commonly undergo N-alkylation or C-alkylation. N-Methyl pyrrole can be prepared by interaction of methyl iodide with potassium pyrrole (40%). N-Carbethoxy pyrrole is made from chloroformic ester and potassium pyrrole. The C-alkylation of pyrroles has been discussed. 3-Alkylindoles are made by the alkylation and decarboxylation of indole-2-carboxylic acid. The conditions for alkylation of pyrrolidine are analogous to those employed for the alkylation of a secondary amine. Thus, pyrrolidine on treatment with n-butyl bromide and potassium hydroxide in boiling benzene is con-... 

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