(Z)-2-(2-Isopropyl-5-methylphenoxy)-N′-(2-oxoindolin-3-ylidene)acetohydrazide

In the title Mannich base, C20H21N3O3, an isatin derivative of thymol, the O—CH2—C(=O)–N(H)—N fragment connecting the aromatic and fused-ring systems is approximately planar, with the N—N single bond in a Z configuration. The amino H atom of this N—N fragment is intramolecularly hydrogen bonded to the carbonyl O atom of the indolinone fused ring as well as to the phenoxy O atom of the aromatic ring. The amino H atom of the indoline fused ring forms a hydrogen bond with the double-bond O atom of an adjacent molecule, this hydrogen bond giving rise to a linear chain motif.

In the title Mannich base, C 20 H 21 N 3 O 3 , an isatin derivative of thymol, the O-CH 2 -C( O)-N(H)-N fragment connecting the aromatic and fused-ring systems is approximately planar, with the N-N single bond in a Z configuration. The amino H atom of this N-N fragment is intramolecularly hydrogen bonded to the carbonyl O atom of the indolinone fused ring as well as to the phenoxy O atom of the aromatic ring. The amino H atom of the indoline fused ring forms a hydrogen bond with the double-bond O atom of an adjacent molecule, this hydrogen bond giving rise to a linear chain motif.
Equimolar quantities of 2-(2-isopropyl-5-methylphenoxy)acetohydrazide (Nargud et al. 1996 andShah et al. 1996) and isatin (0.02 mole) in 50 ml of dioxan were taken in a 100 ml round bottom flask. To this mixture 5 ml of glacial acetic acid was added. The reaction mixture was refluxed for about 2 hours and then cooled. A solid separated was filtered off with suction to isolate the product (82 % yield) and recrystallized in ethanol, yellow crystals suitable for X-ray diffraction were obtained.

Refinement
All H atoms were positioned geometrically, (C-H = 0.93 Å, N-H = 0.86 Å) and refined using a riding model with U iso (H)= 1.2 U eq (C, N) except the two on nitrogen atoms which were located and refined isotropically.  Fig. 1. Molecular structure of (I) with intramolecular hydrogen bonds. Displacement ellipsoids drawn at the 50% probability level, the H atoms involved in intramolecular hydrogen bonds are shown as small spheres of arbitrary radius.

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 Rfactors(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.