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.
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.
Unidad Profesional Interdisciplinaria de Biotecnología del Instituto Politécnico Nacional, Av. Acueducto s/n, Barrio la Laguna Ticomán 07340, México D. F., Mexico.
Itzia I
II
Padilla-Martinez
Irma Y
IY
Flores-Larios
Efren V
EV
García-Baez
Jorge
J
Gonzalez
Alejandro
A
Cruz
Francisco J
FJ
Martínez-Martinez
D001578:Benzopyrans / Q000138:chemical synthesis* / Q000737:chemistry; D003500:Cyclization; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D015394:Molecular Structure; D013055:Spectrophotometry, Infrared; D014965:X-Rays
D001578:Benzopyrans
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