A monoclinic polymorph of 3,7,7-trimethyl-1-phenyl-5,6,7,8-tetrahydro-1H-pyrazolo[3,4-b]quinolin-5-one

Abstract

A second, monoclinic, polymorph of the title compound, C19H19N3O, is reported. In this polymorph, the molecules are linked into chains by paired C-H...pi hydrogen bonds and the chains are linked into sheets by pi stacking interactions.

3-(4-Methoxyphenyl)-7,7-dimethyl-1,6,7,8-tetrahydropyrazolo[3,4-b]quinolin-5-one: a chain of centrosymmetric rings built from N—H...N and C—H...π(arene) hydrogen bonds

“…1), synthesized using microwave irradiation in the absence of solvent. The structures of several analogous compounds have been reported recently, including those of (II), in both triclinic (Low et al, 2003) and monoclinic polymorphs (Mera et al, 2005), (III) (Low et al, 2004) and (IV) (Low et al, 2005), but in none of compounds (II)±(IV) is there an NÐH bond at pyrazole atom N1, as found in compound (I). Hence, the supramolecular aggregation in (I) is necessarily different from those found in (II)±(IV).…”

“…We brie¯y compare here the supramolecular aggregation in compound (I) with that found in each of compounds (II)±(IV). In the monoclinic polymorph of compound (II), which crystallizes with Z H = 1 in the space group P2 1 /n (Mera et al, 2005), two distinct CÐHÁ Á Á% hydrogen bonds link the molecules into chains of rings, which are further linked into sheets by %±% stacking interactions. By contrast, in the triclinic polymorph of (II), which crystallizes with Z H = 2 in the space group P1 (Low et al, 2003), each type of molecule forms a distinct chain built from a combination of CÐHÁ Á ÁO and CÐHÁ Á Á% hydrogen bonds.…”

The crystal structure of 3-chloro-2-(4-methylphenyl)-2H-pyrazolo[3,4-b]quinoline

“…aromatic (Mera et al, 2005;Cruz et al, 2006;Portilla et al, 2007). Similarly, in a series of benzo[f]pyrazolo[3,4-b]quino-]quinolines, in each of which there is a substituent at position 1, but not at position 2, the pyridine ring is fully aromatic (Portilla, Quiroga et al, 2005;Portilla, Serrano et al, 2005;Portilla et al, 2008).…”

Polymorphism and Solvatomorphism 2005

“…The 2005 literature contains a very large number of reports on additional organic compounds that have been shown to exhibit the phenomenon of polymorphism. Many of these substances are probably of limited pharmaceutical interest, but nevertheless some of the reported results71–114 are summarized in Table 1 for those workers who may have a suitably directed interest.…”