Racemic N-methyl-4-[2-(methylsulfanyl)pyrimidin-4-yl]-1-(tetrahydrofuran-3-yl)-1H-pyrazol-5-amine

The title compound, C13H17N5OS, was obtained by cycloaddition of 2-[2-(methylsulfanyl)pyrimidin-4-yl]-3-oxopropanenitrile with (tetrahydrofuran-3-yl)hydrazine dihydrochloride and subsequent N-methylation of 4-[2-(methylsulfanyl)pyrimidin-4-yl]-1-(tetrahydrofuran-2-yl)-1H-pyrazol-5-amine with methyl iodide. The two molecules in the asymmetric unit have opposite absolute configurations and are related by a noncrystallographic inversion center. Both feature intramolecular N—H⋯N hydrogen bonds. The geometry of the molecules is similar to that observed in the structure of a single enantiomer of the title compound.


Related literature
For the structure of the R-enantiomer component of the racemic title compound, see: Liu et al. (2009a). For details of the synthesis of the title compound, see: Liu et al. (2009a,b Table 1 Hydrogen-bond geometry (Å , ).

Comment
The title compound was obtained by cycloaddition of 2-(2-(methylsulfanyl)pyrimidin-4-yl)-3-oxopropanenitrile with (tetrahydrofuran-3-yl)hydrazine dihydrochloride and subsequent N-methylation of 4-(2-(methylsulfanyl)pyrimidin-4-yl) -1-(tetrahydrofuran-2-yl)-1H-pyrazol-5-amine with methyl iodide. As cycloaddition may potentially yield one of the two isomeric products differing in the position of the tetrahydrofuranyl substituent, present study was undertaken to establish which of the isomers is actually formed. The X-ray study showed that the product represents the title compound with amino and tetrahydrofuranyl substituents at the neighbouring atoms of the pyrazolyl ring.
There are two molecules in the asymmetric unit (Fig. 1). The molecules are chemically and conformationally identical, but have opposite absolute configurations; moreover, the structure provides an interesting case of almost precise, though non-crystallographic inversion symmetry. The local inversion center has approximate coordinates of -0.001, 0.134, 0.249.
Such arrangement may be facilitated by the weak interactions between the H atoms of methyl groups C8 and C21 and the π-electron densities of pyrazolyl rings N6-N7-C18-C19-C20 and N1-N2-C5-C6-C7 respectively: the distances between the methyl C atoms and the centroids of the corresponding rings are 3.520 Å and 3.589 Å.
The geometry of the molecules is very similar to that observed in the structure of single enantiomer obtained by chiral separation of the title compound (Liu et al., 2009a). The methylsulfanylpyrimidine group and pyrazolyl ring lie approximately in one plane; maximum deviations of the C10 and C18 atoms in each of the two molecules are 0.033 (2) Å and 0.037 (2) Å respectively; displacements of methyl C8 and C21 atoms are 0.967 (2) Å and 1.020 (2) Å. Orientation of the tetrahydrofuran ring can be characterized by the dihedral angles 75.6 (1)° and 77.8 (1) formed by the pyrimidine-pyrazolyl planes with the C2-C3-C4 and C15-C16-C17 planes in each of the two molecules respectively.
The secondary amino groups in both molecules (N3 and N8) form intramolecular H-bonds with the N atoms of the pyrimidine rings (N5 and N10 respectively; Table 2).

Experimental
The detailed descriptions of the synthesis of the title compound are given in Liu et al. (2009a) and Liu et al. (2009b).