Badger, G. M. published the artcilePorphyrins. V. The cyclization of linear tetrapyrroles, Recommanded Product: 2,4-Dimethyl-1H-pyrrole-3-carbonitrile, the publication is Australian Journal of Chemistry (1964), 17(9), 1013-21, database is CAplus.
cf. CA 61, 13265c. Tetrapyrrenes (I) were prepared by condensation of 3-acetyl-2,4-dimethylpyrrole (II) or of 3-cyano-2,4-dimethylpyrrole (III) with 5,5′-bis(methoxymethyl)-3,3′,4,4′-tetramethyldipyrromethane-HBr (IV). A mixture of 100 g. 5-ethoxycarbonyl-2,3,4trimethylpyrrole, 100 ml. 98% HCO2H, and 100 ml. 48% HBr was heated 8 hrs. on a steam bath and left overnight to yield 83 g. 3,3′,4,4′,5,5′-hexamethyldipyrromethene-HBr (V), m. 308-10°. Br (16 g.) in 20 ml. HOAc was added during 30 min. to a stirred and heated mixture (70-5°) of 12 g. V in 100 ml. HOAc, and the mixture stirred 30 min. at 75° and cooled to yield 15 g. 5,5′-bis(bromomethyl)-3,3′,4,4′-tetramethyldipyrromethene-HBr (VI), m. >300°. VI (5 g.) in 50 ml. MeOH was refluxed 30 min., the solution cooled, 100 ml. ether added, the mixture left overnight at 0° the separated product dissolved in boiling C6H6, and the solution diluted with boiling petr. ether and cooled to yield 2.7 g. IV, m. 174-6°. The oxime of 2-ethoxycarbonyl-4-formyl-3,5-dimethylpyrrole was converted into the nitrile, mild alk. hydrolysis of which yielded 5-carboxy-3-cyano-2,4-dimethylpyrrole, which on decarboxylation by refluxing 1 hr. with ethanolamine yielded III, m. 107°. A solution of 1 g. IV and 0.75 g. II in 20 ml. C6H6 was refluxed 1 hr. and cooled to yield 0.92 g. I.HBr (R = Ac) (VI), m. 235° [decomposition, darkening at 225° (CHCl3-petr. ether]. Similarly, 1.5 g. IV and 1 g. III in 30 ml. C6H6 was refluxed 1 hr., cooled, diluted with 15 ml. ether, and refrigerated to yield I.HBr (R = CN) (VII), m. 235-40° (decomposition) (CHCl3-petr. ether). VI (0.I g.) was dissolved in 100 ml. MeOH, the mixture refluxed 1 hr., 0.2 g. Cu(OAc)2 added, the mixt refluxed 48 hrs., MeOH evaporated, the residue extracted 3 hrs. (Soxhlet) with CHCl3, the CHCl3 extract concentrated, the residue dissolved in concentrated H2SO5, the solution left 3 hrs. at room temperature, poured on ice, the mixture extracted with CHCl3, and the extract washed with NH4OH, H2O, dried, and chromatographed over grade IV Al2O3, using CHCl3-petr. ether for elution. The red band exhibiting red fluorescence was eluted first, and the solution evaporated to give 1,2 – diacetyl – 3,4,5,6,7,8- hexamethylporphine (VIII), which was dissolved in CHCl3, λ 420, 518, 556, 588 and 642.7 m. A portion of this solution was evaporated, the residue dissolved in 4:1 C5H5N-H2O, NH2OH.HCl added, and the mixture heated 30 min. on a steam-bath. The resulting solution showed λ 505, 537.5, 572.5 and 625.8 mμ. A 2nd portion of the CHCl3 solution was evaporated, the residue dissolved in dioxane, aqueous NaBH4 solution added, the mixture left overnight, worked up, and the product taken up in CHCl3, washed with NH4OH, H2O, and dried. The resulting solution had 501.7, 534.2,568.3 and 623.3 mμ. Alternatively, 2 g. 1′,1,8′-dideoxy-1′,2,3,4,5,6,7,8′-octamethylbilene-b-HBr was dissolved in 1 l. MeOH by refluxing 1 hr., 4 g. Cu(OAc)2 added, the mixture refluxed 1 week and filtered, the residue extracted 1 hr. (Soxhlet) with MeOH, the extract filtered (Celite), and the residue and Celite extracted again (Soxhlet) with CHCl3 2 hrs. (extract A) and then with fresh CHCl3 for 18 hrs. (extract B). Cohen. of extract B yielded 0.05 g. VIII Cu complex, m. 316-18° (decomposition). Extract A was evaporated, the residue dissolved in 20 ml. concentrated H2SO4, the mixture left 1 hr., poured on 400 g. crushed ice and the separated solid extracted (Soxhlet) with CHCl3 Evaporation of the CHCl3 extract yielded 0.08 g. VIII, m. >360° as steel-blue-needles. Cyclization of VII under similar conditions gave 2 porphyrins, presumably 1-cyano-3,4,5,6,7,8hexamethylporphine (λ 412,516.2, 522,571,621 and 636 mμ) and 1,2-dicyano-3,4,5,O,7,8-hexamethylporphine (λ 420, 519, 555, 590.2 and 643.5 mμ) in poor yield.
Australian Journal of Chemistry published new progress about 26187-28-0. 26187-28-0 belongs to nitriles-buliding-blocks, auxiliary class Pyrrole,Nitrile, name is 2,4-Dimethyl-1H-pyrrole-3-carbonitrile, and the molecular formula is C7H8N2, Recommanded Product: 2,4-Dimethyl-1H-pyrrole-3-carbonitrile.
Referemce:
https://en.wikipedia.org/wiki/Nitrile,
Nitriles – Chemistry LibreTexts