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Molecules 2011, 16(1), 915-932; doi:10.3390/molecules16010915
Article

X-Ray Supramolecular Structure, NMR Spectroscopy and Synthesis of 3-Methyl-1-phenyl-1H-chromeno[4,3-c]pyrazol-4-ones Formed by the Unexpected Cyclization of 3-[1-(Phenyl-hydrazono)ethyl]-chromen-2-ones

1
, 2, 1, 2, 1 and 2,*
Received: 16 December 2010; in revised form: 8 January 2011 / Accepted: 18 January 2011 / Published: 21 January 2011
(This article belongs to the Section Organic Synthesis)
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Abstract: The molecular structures of nine 3-methyl-1-phenyl-1H-chromeno[4,3-c]pyrazol-4-one isomers, obtained by the oxidative cyclization of the corresponding 1-phenylhydrazono chromen-2-ones with copper acetate as catalyst, are reported. The molecular and supramolecular structures of the 8-chloro, 8-bromo- and 8-nitro isomers 2b-d, were established by X-ray diffraction. The halogenated isomers 2b and 2c are isomorphs, they crystallize as a triclinic system, space group P-1 with two molecules in the asymmetric unit. Compound 2d crystallizes as a monoclinic system, space group P21/m with two molecules in the unit cell. The 1-phenyl ring [Cg(4)] is almost perpendicularly positioned to the chromene-pyrazole ring system. This conformation is in agreement with the anisotropic NMR shielding effect exerted by the phenyl ring over H-9 in solution. The supramolecular architecture is almost controlled by C―H···A (A = O, p) and face to face p-stacking interactions. The observed p-stacking trend between chromene and pyrazole rings is given by the overlapping between the best donor and acceptor rings in each compound.
Keywords: oxidative cyclization; benzopyrano-arylhydrazone; benzopyrano-pyrazolone; pi-stacking oxidative cyclization; benzopyrano-arylhydrazone; benzopyrano-pyrazolone; pi-stacking
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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MDPI and ACS Style

Padilla-Martinez, I.I.; Flores-Larios, I.Y.; García-Baez, E.V.; Gonzalez, J.; Cruz, A.; Martínez-Martinez, F.J. X-Ray Supramolecular Structure, NMR Spectroscopy and Synthesis of 3-Methyl-1-phenyl-1H-chromeno[4,3-c]pyrazol-4-ones Formed by the Unexpected Cyclization of 3-[1-(Phenyl-hydrazono)ethyl]-chromen-2-ones. Molecules 2011, 16, 915-932.

AMA Style

Padilla-Martinez II, Flores-Larios IY, García-Baez EV, Gonzalez J, Cruz A, Martínez-Martinez FJ. X-Ray Supramolecular Structure, NMR Spectroscopy and Synthesis of 3-Methyl-1-phenyl-1H-chromeno[4,3-c]pyrazol-4-ones Formed by the Unexpected Cyclization of 3-[1-(Phenyl-hydrazono)ethyl]-chromen-2-ones. Molecules. 2011; 16(1):915-932.

Chicago/Turabian Style

Padilla-Martinez, Itzia I.; Flores-Larios, Irma Y.; García-Baez, Efren V.; Gonzalez, Jorge; Cruz, Alejandro; Martínez-Martinez, Francisco J. 2011. "X-Ray Supramolecular Structure, NMR Spectroscopy and Synthesis of 3-Methyl-1-phenyl-1H-chromeno[4,3-c]pyrazol-4-ones Formed by the Unexpected Cyclization of 3-[1-(Phenyl-hydrazono)ethyl]-chromen-2-ones." Molecules 16, no. 1: 915-932.


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