Structures of three methoxy-substituted benzaldehyde 7-chloro-1-methyl-4H-quinolinyl-4-ylidene-hydrazones: variations in π···π interactions

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Abstract

Three crystal structures are reported here: (E,E)-arenecarbaldehyde 7-chloro-1-methyl-4H-quinolinyl-4-ylidene-hydrazones, 3, [arenecarbaldehyde = 3-MeOC₆H₄CHO (3a), 3,4-(MeO)₂C₆H₃CHO (3b) and 2,3-(MeO)₂C₆H₃CHO (3c)]. While in each compound π···π stacking and other intermolecular interactions make contributions to the overall supramolecular arrangements, very different arrangements result for the relatively flat molecules of 3a and 3b and the non-planar molecules of 3c. In 3a, all possible π···π interactions [π(quin)···π(quin), π(quin)···π(phen) and π(phen)···π(phen)] are present and together generate a sheet of molecules, one molecule thick) [quin = quinolinyl; phen = methoxyphenyl]. In 3b, π(phen)···π(phen)] interactions are absent: however, π(quin)···π(quin) and π(quin)···π(phen) interactions are both involved in producing a column of molecules, two molecules wide. In 3c, two distinct dimeric π···π stacked structural subsets are formed: (i) one dimer is composed of the two independent molecules, A and B, and generated from π(quin)···π(quin) interactions and (ii) the other AB dimeric unit is formed from π(phen)···π(phen) interactions. The differences in the π···π intermolecular interactions found in 3a, 3b and 3c are consequences of the steric effects presented by the methoxy substituents in the phenyl ring.

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Keywords: crystal structures; hydrazones; quinoline derivatives; π···π stacking interactions Document Type: Research Article DOI: 10.1515/zkri-2015-1848 Publication date: 1 de Maio de 2015

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Abstract

Reactions between either L-serine methyl ester hydrochloride (1), or the cbz derivative, methyl (S)-(+)-2-(benzyloxycarbonylamino)-3-hydroxypropanoate (2), and pyrazinoyl chloride (3), have been studied. Methyl (S)-(+)-2-benzyloxycarbonylamino-3-[(pyrazinecarbonyl)oxy]propionate (4), methyl (S)-(+)-3-hydroxy-2-[(pyrazine-2-carbonyl)amino]propionoate (7), methyl 2-[(pyrazinecarbonyl)amino]acrylate (8) were obtained. Additional products, methyl (S)-(+)-2-benzyloxycarbonylamino-3-formyloxypropionoate (5) and methyl (R)-(+)-2-benzyloxycarbonylamino-3-chloropropionoate (6), were isolated from reaction of 2 with 3, in the presence of DMF remaining from the preparation of 3, from pyrazinecarboxylic acid. The coupling of pyrazinecarboxylic acid with 1, in the presence of DCC was prevented by the formation of the unreactive adduct between DCC and pyrazinoic acid. The compounds were tested against M. tuberculosis: compounds (8) and (6) exhibited a MIC (μg/ml) value of 50 and 100, respectively, compared to the MIC value of 100 for the first line TB drug, pyrazinamide. The confirmation of the structure of (8) was obtained via X-ray crystallography.

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Keywords: SYNTHESIS, TUBERCULOSIS, L-SERINE DERIVATIVES, PYRAZINOIC ACID DERIVATIVES, CRYSTAL STRUCTURE, DIDEHYDROAMINO ACID Document Type: Research Article DOI: http://dx.doi.org/10.3184/030823407X200001 Publication date: 1 de Março de 2007 [:en]

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Abstract

Three crystal structures are reported here: (E,E)-arenecarbaldehyde 7-chloro-1-methyl-4H-quinolinyl-4-ylidene-hydrazones, 3, [arenecarbaldehyde = 3-MeOC₆H₄CHO (3a), 3,4-(MeO)₂C₆H₃CHO (3b) and 2,3-(MeO)₂C₆H₃CHO (3c)]. While in each compound π···π stacking and other intermolecular interactions make contributions to the overall supramolecular arrangements, very different arrangements result for the relatively flat molecules of 3a and 3b and the non-planar molecules of 3c. In 3a, all possible π···π interactions [π(quin)···π(quin), π(quin)···π(phen) and π(phen)···π(phen)] are present and together generate a sheet of molecules, one molecule thick) [quin = quinolinyl; phen = methoxyphenyl]. In 3b, π(phen)···π(phen)] interactions are absent: however, π(quin)···π(quin) and π(quin)···π(phen) interactions are both involved in producing a column of molecules, two molecules wide. In 3c, two distinct dimeric π···π stacked structural subsets are formed: (i) one dimer is composed of the two independent molecules, A and B, and generated from π(quin)···π(quin) interactions and (ii) the other AB dimeric unit is formed from π(phen)···π(phen) interactions. The differences in the π···π intermolecular interactions found in 3a, 3b and 3c are consequences of the steric effects presented by the methoxy substituents in the phenyl ring.

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Keywords: crystal structures; hydrazones; quinoline derivatives; π···π stacking interactions Document Type: Research Article DOI: 10.1515/zkri-2015-1848 Publication date: 1 de Maio de 2015 [:]