2-Hydroxy-2-methyl-1-phenylindolin-3-one

In the title compound, C15H13NO2, the indole and benzene rings make a dihedral angle of 60.61 (4)°. In the crystal, dimeric pairs (twofold symmetry) are formed via O—H⋯O hydrogen bonds.

In the title compound, C 15 H 13 NO 2 , the indole and benzene rings make a dihedral angle of 60.61 (4) . In the crystal, dimeric pairs (twofold symmetry) are formed via O-HÁ Á ÁO hydrogen bonds.

Related literature
For naturally occurring 2-hydroxyindol-3-ones, see: Bhakuni et al. (1991). For intermediates of the 2-hydroxyindol-3-one substructure in the total syntheses of some natural products including (+)-isatisine A, (AE)-mersicarpine, hinckdentine A, mitomycin and others, see   Table 1 Hydrogen-bond geometry (Å , ). Financial support from the Ministry of Education, Youth and Sports of the Czech Republic (project MSM7088352101) and the Slovenian Research Agency (programme P1-0230-0103, programme-0175, joint project BI-CZ/07-08-018 and joint project Nr 9-06-3 of programme KONTAKT) is gratefully acknowledged. This work was also partly supported through the infrastructure of the EN-FIST Centre of Excellence, Ljubljana.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: TK5007).

Experimental
A mixture of 3-hydroxy-3-methyl-1-phenylquinoline-2,4(1H,3H)-dione (1.34 g, 5.0 mmol) in 1.3 M aqueous potassium hydroxide (30 ml) and benzene (120 ml) was vigorously stirred in the presence of air at room temperature for 30 min. Layers were separated, and the aqueous phase was extracted with benzene (5 x 20 ml). The combined organic layer was dried over K 2 CO 3 . The solvent was evaporated to dryness and the residue was crystallized from a mixture of benzene and cyclohexane to give crystals of the title compound (0.62 g, 2.6 mmol, 52%).

Refinement
All H atoms were positioned geometrically and refined using a riding model, with C-H bond lengths constrained to 0.93   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 > 2σ(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.