5-[(tert-Butyldiphenylsilyloxy)methyl]pyridazin-3(2H)-one

In the title compound, C21H24N2O2Si, a new pyridazin-3(2H)-one derivative, the carbonyl group of the heterocyclic ring and the O atom of the silyl ether are located on the same side of the pyridazinone ring and the C—C—O—Si torsion angle is −140.69 (17)°. In the crystal, molecules are linked by pairs of strong N—H⋯O hydrogen bonds into centrosymmetric dimers with graph-set notation R 2 2(8). Weak C—H⋯π interactions are also observed.

In the title compound, C 21 H 24 N 2 O 2 Si, a new pyridazin-3(2H)one derivative, the carbonyl group of the heterocyclic ring and the O atom of the silyl ether are located on the same side of the pyridazinone ring and the C-C-O-Si torsion angle is À140.69 (17) . In the crystal, molecules are linked by pairs of strong N-HÁ Á ÁO hydrogen bonds into centrosymmetric dimers with graph-set notation R 2 2 (8). Weak C-HÁ Á Á interactions are also observed.

Comment
Pyridazin-3(2H)-ones constitute an attractive building block for the designing and synthesis of new drugs. In many cases, the incorporation of a pyridazinone fragment in established biologically active molecules provides useful ligands for different targets. Thus, pyridazinone derivatives possess a wide variety of pharmacological properties, such as antihypertensive (Siddiqui et al., 2010), cardiotonic (Moos et al., 1987) and antiplatelet activities (Coelho et al., 2007) and many of them have also been reported as anti-inflammatory (Abouzid & Bekhit, 2008), antinociceptive (Cesari et al., 2006), antidiabetic (Rathish et al., 2009), anticonvulsant (Sivakumar et al., 2003), anticancer (Al-Tel, 2010), antimicrobial (Suree et al., 2009) or anti-histamine H 3 agents (Tao et al., 2011). Most of pyridazinone derivatives previously described are 6-arylpyridazin-3(2H)-ones, a structure which was considered essential for cardiotonic and antiplatelet activities resulting from phosphodiesterase III inhibition (Weishaar et al., 1985). However, the replacement of aryl by an alkyl chain functionalized with alcohol or ether groups gave rise to potent antiplatelet agents with a different mechanism of action (Costas et al., 2010). In order to discover new pyridazinone analogues with this kind of activity, the titled compound I was synthesized and its crystal structure was determined.
The molecular structure of compound I, a new pyridazin-3(2H)-one derivative C5 substituted, is shows in figure 1. In the title compound the carbonyl group of the heterocyclic ring and the oxygen atom of the silyl ether are placed on the same side same side of the pyridazinone ring and the C5-C1′-O1′-Si torsion angle is -140.69 (17)°. The pyridazinone ring, a planar moiety, forms dihedral angles of 71.59 (10)° and 47.50 (10)°, respectively, with the C2′-C7′ and C8′-C13′ benzene rings, while the dihedral angle between both benzene rings is 73.07 (14)°. In the crystal structure the molecules are linked by N-H···O hydrogen bond interaction forming centrosymmetric ring with set-graph motif R 2 2 (8), (Bernstein et al., 1995), (Figure 2), Table 1. Weak C-H···π interactions are also observed

Refinement
All H-atoms were positioned and refined using a riding model with d(C-H)= 0.93 Å, U iso = 1.2U eq (C) for aromatic C-H groups,d(C-H)= 0.97 Å, U iso = 1.2U eq (C) for CH 2 group and d(C-H)= 0.96 Å, U iso = 1.5U eq (C) for CH 3 group; except for the hydrogen atoms of the NH group which were located from a Fourier-difference map and refined isotropically. The poor quality of the crystal, detected by its high mosaicity, explains the high value of the anisotropic displacement supplementary materials sup-2 Acta Cryst. (2013). E69, o1826-o1827 parameters corresponding to certain atoms, such as C4′, C10′, C11′, C12′, C17′. However, both data and model are good enough for a correct study.

Figure 1
The molecular structure of (I) showing the atom-numbering scheme. Displacement ellipsoids are shown at the 20% probability level.  View of supramolecular dimer generated by NH···O hydrogen bonds. Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.