Pyrrole, l-

Bis(3,4-diethyl-2-pyrrolylmethyl)-3,4-dietliyl-l//-pyrrole (2), prepared in situ from the di-t-butylester of the 5,5 -dicarboxylic acid (/), reacts with 4//-1,2,4-triazole-3,5-dialdehyde (3) in di-chloromethane in the presence of trifluoroacetic acid and 2,3-dichloro-5,6-dicyano-/)-benzoquino-ne as an oxidation reagent. Dark blue crystals are obtained after chromatographic purification. The dark violet chloroform solution fluoresces purple at 360 nm and gives the NMR experiments 39. Which compound and which tautomer of it has been formed ... 

As has been pointed out earlier (76AHCS1, p. 215), l//-pyrrole la and its simple derivatives are far more stable than the corresponding pyrrolenine forms lb and Ic. Recent studies confirm these experimental results (90HC1,90HC549 see also 82JOC5132 97MI1). 

Diazo-coupling products of 1-substituted l//-pyrrol-3(2//)-ones have been shown by X-ray crystallography to adopt the hydrazone structure 115 [91JCS(P1)701]. 

CN 6-(dimethylamino)-2-[2-(2,5-dimethyl-1 -phenyl- l//-pyrrol-3-yl)ethenyl]-1 -methylquinolinium 4,4 -... 

CN A-[5-[[(3-amino-3-iminopropyl)amino]carbonyl]-l-methyl-l//-pyrrol-3-yl]-4-[[[4-(rormylamino)-methyl-l//-pyrrol-2-yl]carbonyl]amino]-l-methyl-lf/-pyrrole-2-carboxamide... 

RN 33369-31-2 MF Ci5H,4ClN03 MW 291.73 EINECS 251-474-2 CN 5-(4-chlorobenzoyl)-l,4-dimethyl-l//-pyrrole-2-acetic acid... 

Methyl 3-acyl-l-diphenylmethyleneamino-4,5-dioxo-4,5-dihydro-l//-pyrrole-2-carboxylates 489 are formed from 488 and oxalyl chloride in good yields. Preparative thermolysis of these compounds at 130-140°C gives mixtures of dipyrazolo[l,2- l,2- [l,2,4,5]tetrazines 491 as major products and pyrazoles 492 as minor hydrolytic by-products. The intermediacy of mesoionic compound 490 is expected (Scheme 83) <2004T5319>. 

Polymeric films of [(//5-C s Me5)M(L)Cl]+complexes (M = Ir, Rh L = pyrrole-substituted bpy or phen) have been coated on an electrode by oxidative electropolymerization. The buildup of hydrido complexes in films is well known 27,28,30 the high electrocatalytic activity of these molecular electrode materials towards dihydrogen evolution in organic and aqueous electrolytes is also well known.25,31 For example, H2 is evolved at —0.55 V vs. SCE at a poly [(j75-C5Me5)-Rh(bpy)Cl]+ film in pH 1 aqueous solution.31... 

These compounds are first characterised by their magnetic behaviour. The spin-only high spin value of Fe(III) is 5.92 B.M., while a normal range for its low spin values in cubic symmetry is 2.0-2.3 B.M. [24-26]. Among the compounds listed in Table 1, these extreme cases are met by the low spin tris(l-pyrrole-dithiocarbamato)iron(III) hemikis(dichloromethane)... 

The difference between the Fe-S bond lengths in the high spin and low spin states is about 0.15 A, which is also in line with the Fe-S bond lengths for the low spin tris(l-pyrrole-dithiocarbamato)iron(III) hemikis(dichloro-... 

The silyloxypyrrole 309 was prepared in 91% yield from the ,/3-unsaturated lactam 308 with TBDMSOTf and 2,6-lutidine (Equation 54) <1999TL2525>. Alternatively, the pyrrolo[l,2-f]oxazoles derivatives 311 were prepared by reaction between the stable bcnzotriazol-1 -yl(l //-pyrrol-2-yl)methanone 310 and various ketones (Equation 55) <2004JOC9313>. These two examples are the rare representatives of the pyrrolo[l,2-r ]oxazole ring system described in the literature to date. 

The most successful modifier is cinchonidine and its enantiomer cinchonine, but some work in expanding the repertoire of substrate/modifier/catalyst combinations has been reported (S)-(-)-l-(l-naphthyl)ethylamine or (//)-1 -(I -naphth T)eth Tamine for Pt/alumina [108,231], derivatives of cinchona alkaloid such as 10,11-dihydrocinchonidine [36,71], 2-phenyl-9-deoxy-10, 11-dihydrocinchonidine [55], and O-methyl-cinchonidine for Pt/alumina [133], ephedrine for Pd/alumina [107], (-)-dihydroapovincaminic acid ethyl ester (-)-DHVIN for Pd/TiOz [122], (-)-dihydrovinpocetine for Pt/alumina [42], chiral amines such as 1 -(1 -naphtln I)-2-(I -pyrro 1 idiny 1) ethanol, l-(9-anthracenyl)-2-(l-pyrrolidinyl)ethanol, l-(9-triptycenyl)-2-(l-pyrrol idi nyl)cthanol, (Z )-2-(l-pyrrolidinyl)-l-(l-naphthyl)ethanol for Pt/alumina [37,116], D- and L-histidine and methyl esters of d- and L-tryptophan for Pt/alumina [35], morphine alkaloids [113],... 

The synthesis of chiral pyrroloketopiperazines 174 was achieved via diastereo-selective Ugi reaction, with chiral 2-(2-formyl-l//-pyrrol-l-yl)acetic acids 175 conveniently derived from ot-amino acids [54]. The reaction proceeds with moderate diastereoselectivity trans. cis, up to 4 1) to give the target compounds 174 in good yields (Scheme 30). Noteworthy, the mixture of diastereomeres was separated by column chromatography and could be isolated as single diastereomeres. 

Scheme 49 Four-component synthesis of 4,5-dthydro-l//-pyrrol-3-carboxamide derivatives...

Activation of the carboxylic acid function of 2-(l//-pyrrol-l-yl)isoindolin-l-one 253 yielded 5,5a-dihydropyrro-lo[l, 2 2,3]pyridazino[6,l- ]isoindole-4,10-dione 254 (Equation 64) <1995H(41)689>. 

III) 2-(4-Fluorophenyl)-P,5-dihydroxy-5-(l-methylethyl)-3-phenyl-4-[(phenylamino)carbonyl]-l//-pyrrole-heptanoic acid. 

Finally, ortho aminoesters have been used to produce 7-deazaxanthines. For example ethyl 2-amino-5-phenyl-l//-pyrrole-3-carboxylate is first treated with 2-chloroethyl isocyanate in refluxing toluene. The resulting urea derivative is then allowed to react with l-(2-methoxyphenyl)piperazine and cyclized to the expected pyrrolo[2,3-,7 pyrimidin-2,4(177,377)-dione <2006BMCL150>. 

The allylically activated chiral methanimidamides are more reactive and can be prepared from 2,5-dihydro-l//-pyrrole or 1,2,5,6-tetrahydropyridine by heating with a chiral auxiliary substituted methanimidamide in toluene. Deprotonation of the more acidic 1 -iminomethy 1-2,5-dihydro-1//-pyrrole with butyllithium was complete after a few minutes, even at — 100 °C41. Alkylation afforded a mixture of regioisomers, 2-alkylated 2,5-dihydro-l //-pyrrole 1 (n = 1) and 3-alkylated 2,3-dihydro-l//-pyrrole 2 (n = 1), the former strongly predominating (about 92 8). During hydrazinolysis of the 2-substituted 2,5-dihydro-1 //-pyrrole 1 (n = 1) the minor product decomposed, thus separation of the regioisomers was unnecessary. About 80-85% of the chiral auxiliary (S)-l- m-butoxy-3-methyl-2-butanamine was recovered after hydrazinolysis. 

Catalytic hydrogenation of 2-alkyl-2,5-dihydro-l//-pyrrole with 5% rhodium on carbon gave 2-substituted pyrrolidines in 95-96% ee (Pirkle analysis42) without attendant racemization. 

To a 0.02 M soln of 2-alkyl-2,5-dihydro-l //-pyrrole (85-90% pure) in methanol is added with stirring 5% rhodium on carbon (catalyst/substrate 1 20). The mixture is pressurized (4.6 x 107 Torr) with hydrogen and is stirred at 25 °C for a minimum of 5 h. The catalyst is removed by vacuum filtration, the solution is concentrated under reduced pressure and the residue is purified by bulb-to-bulb distillation to give the product in 95% purity. 

Porphobilinogen (5-amino-4-carboxymethyl-l//-pyrrole-3-propionic acid) [487-90-1 ]M... 

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