ChemInform Abstract: Pyrrolodiazines. Part 4. Structure and Chemistry of 3,4-Dihydropyrrolo( 1,2-a)pyrazine (original) (raw)
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Pyrrolodiazines. 4. Structure and chemistry of 3,4-dihydropyrrolo[1,2-a]pyrazine
Tetrahedron, 1997
Abtra~ The structure of 3,4-dihydropyrrolo[ 1,2-a]pyrazine and its N-protonated form is studied by ab initio calculations. Examples of the re, activity of this poorly studied system are presented in which it is shown that the imino moiety does not react with dienes but does undergo inter-and intramolecular 1,3-dipolar cycloadditions by reaction of azomethine ylides of this bicyclic system with suitable dipolarophiles.
The Journal of Organic Chemistry, 1996
A new synthesis of the pyrrolo[1,2-a]pyrazine system from pyrrole is described. In light of the ab initio calculations carried out on this heterocyclic system some of its basic chemistry was investigated and included electrophilic substitution, addition of organolithium reagents, metalation with lithium diisopropylamide and subsequent reaction with electrophiles, and formation of salts by quaternization of the nonbridgehead nitrogen. N-ylides obtained from these salts undergo 1,3-dipolar cycloaddition with suitable dipolarophiles to give dipyrrolo[1,2-a]pyrazines, pyrazolo[1,5-a]-pyrrolo-[2,1-c]pyrazines, and heterobetaines. Examples of intramolecular 1,3-dipolar cycloadditions are also reported.
The Journal of Organic Chemistry, 2004
The palladium-catalyzed Suzuki cross-coupling reaction of arylboronic acids and 6-bromo-and 6,8dibromo-3,4-dihydropyrrolo[1,2-a]pyrazines afforded 6-substituted and 6,8-disubstituted 3,4-dihydropyrrolo[1,2-a]pyrazines in good yields. Stille and Negishi coupling reactions have been used to prepare 6-heteroaryl-substituted derivatives in moderate yields by employing heteroaryl halides and 6-metalated 3,4-dihydropyrrolo[1,2-a]pyrazines as reaction partners. A variety of cyclic secondary amines have also been incorporated at position C-6 of 6-bromo-1-phenyl-3,4-dihydropyrrolo[1,2-a]pyrazine in the presence of the palladium catalyst Pd 2 (dba) 3 in conjunction with BINAP as ligand. This amination reaction is one of the few reported examples of such a palladium-catalyzed transformation on a pyrrole ring, although the reaction could not be extended to less nucleophilic amines. Ettouati, L.; Litaudon, M.; Blunt, J. W.; Munro, M. H. G.; Parkin, S.; Hope, H. Tetrahedron 1994, 50, 3987. (b) Trimurtuhu, G.; Faulkner, D. J.; Perry, N. B.; Ettouati, L.; Litaudon, M.; Blunt, J. W.; Munro, M. H. G.; Jameson, G. B. Fernandez, D.; Danelon, G.; Cuevas, C.; Manzanares, I.; Albericio, F.; Joule, J. A.; Alvarez, M. Voronina, T. A.; Likhosherstov, A. M.; Peresada, V. P.; Moladavkin, G. M.; Halikas, J. A. U.S. Patent 5378846, 1995.
ChemInform, 2005
The palladium-catalyzed Suzuki cross-coupling reaction of arylboronic acids and 6-bromo-and 6,8dibromo-3,4-dihydropyrrolo[1,2-a]pyrazines afforded 6-substituted and 6,8-disubstituted 3,4-dihydropyrrolo[1,2-a]pyrazines in good yields. Stille and Negishi coupling reactions have been used to prepare 6-heteroaryl-substituted derivatives in moderate yields by employing heteroaryl halides and 6-metalated 3,4-dihydropyrrolo[1,2-a]pyrazines as reaction partners. A variety of cyclic secondary amines have also been incorporated at position C-6 of 6-bromo-1-phenyl-3,4-dihydropyrrolo[1,2-a]pyrazine in the presence of the palladium catalyst Pd 2 (dba) 3 in conjunction with BINAP as ligand. This amination reaction is one of the few reported examples of such a palladium-catalyzed transformation on a pyrrole ring, although the reaction could not be extended to less nucleophilic amines. Ettouati, L.; Litaudon, M.; Blunt, J. W.; Munro, M. H. G.; Parkin, S.; Hope, H. Tetrahedron 1994, 50, 3987. (b) Trimurtuhu, G.; Faulkner, D. J.; Perry, N. B.; Ettouati, L.; Litaudon, M.; Blunt, J. W.; Munro, M. H. G.; Jameson, G. B. Fernandez, D.; Danelon, G.; Cuevas, C.; Manzanares, I.; Albericio, F.; Joule, J. A.; Alvarez, M. Voronina, T. A.; Likhosherstov, A. M.; Peresada, V. P.; Moladavkin, G. M.; Halikas, J. A. U.S. Patent 5378846, 1995.
6 H -indeno[1,2- b ]pyrido[3,2- e ]pyrazines. A new heterocyclic ring system
Journal of Heterocyclic Chemistry, 1972
GH-Indeno[ 1,2-b] pyrido[ 3,2-el pyrazines. Condensation of 1,2-indanedione and 1,2,34ndanetrione hydrate (ninhydrin) with 2,3-diaminopyridines gave a number of compounds belonging to the hitherto unknown 6H-indeno[ 1,241pyrido[ 3,2-e ] pyrazinc ring system. The unsymmetrical nature of the reactants can theoretically result in isomeric ring closure products. Assignment of the 6Hring system was based upon the identity of 6H-indeno[ 1,2-b]pyrido[ 3,2-e]pyrazin-6-one obtained from 2,3-diaminopyridine and ninhydrin with material prepared by unequivocal synthesis. The direction of cyclization of ninhydrin and 1,2-indanedione with the diamines was shown to be the same by reduction of the indenopyridopyrazinones to the corresponding indcnopyridopyrazincs. Some physical, chemical, and tumor growth-inhibitory properties of the products are reported.
1, 2-Dihydropyrido [3, 4-b] pyrazines: structure-activity relationships
Journal of Medicinal …, 1983
Certain derivatives containing the 1,2-dihydropyrido[3,4-blpyrazine (l-deaza-7,8-dihydropteridine) ring system are active against experimental neoplasms in mice. The mechanism of action of these agents has been attributed to the accumulation of cells at mitosis. Identification of the structural features that are necessary for activity was accomplished by evaluation of modified 1-deazapteridines and ring and ring-opened analogues. Relative to ethyl
Journal of Organic Chemistry, 2008
The tandem iminium cyclization and Smiles rearrangement of pyridinyloxyacetaldehyde 1 and a primary amine generated a novel pyrido[2,3-e]pyrrolo[1,2-a]pyrazine scaffold. TFA was discovered to be an efficient catalyst in the reactions with aromatic amines, whereas TiCl 4 was found to be superior in the case of aliphatic amines. This methodology proved to be efficient in the preparation of a library of diversified pyrido [2,3-e]pyrrolo[1,2-a]pyrazine derivatives. Novel fused heterocyclic systems are often considered important scaffolds in medicinal chemistry. 1 Heterocyclic compounds possessing a pyrrolo[1,2-a]pyrazine moiety are of biological interest. For example, pyrrolo[1,2-a]quinoxalinones are reported to have oral antiallergic activity, 2 and thieno[3,2e]pyrrolo[1,2-a]pyrazines 3 and pyrido[2,3-e]pyrrolo[1,2-a]pyrazines 4 have been shown to be selective 5-HT 3 receptor agonists. However, few synthetic methodologies to access pyrido[2,3-e]pyrrolo[1,2-a]pyrazines are available. 4,5
Dimethyl and diethyl esters of 5,6-bis(pyridin-2-yl)pyrazine-2,3-dicarboxylic acid: a comparison
Acta Crystallographica Section E Crystallographic Communications, 2016
In dimethyl 5,6-bis(pyridin-2-yl)pyrazine-2,3-dicarboxylate, C18H14N4O4, (I), and diethyl 5,6-bis(pyridin-2-yl)pyrazine-2,3-dicarboxylate, C20H18N4O4, (II), the dimethyl and diethyl esters of 5,6-bis(pyridin-2-yl)pyrazine-2,3-dicarboxylic acid, the orientation of the two pyridine rings differ. In (I), pyridine ringBis inclined to pyrazine ringAby 44.8 (2)° and the pyridine and pyrazine N atoms aretransto one another, while pyridine ringCis inclined to the pyrazine ring by 50.3 (2)°, with the pyridine and pyrazine N atomscisto one another. In compound (II), the diethyl ester, which possesses twofold rotation symmetry, the pyridine ring is inclined to the pyrazine ring by 40.7 (1)°, with the pyridine and pyrazine N atomstransto one another. In the crystal of (I), molecules are linked by C—H...N hydrogen bonds, forming chains along [001]. The chains are linked by C—H...π interactions, forming a three-dimensional structure. In the crystal of (II), molecules are linkedviaC—H...O hydrogen...