Ethyl 4-methyl-1,3-dioxo-1,2,3,4-tetrahydroisoquinoline-4-carboxylate

In the title compound, C13H13NO4, the fused-ring system is nearly planar, with an r.m.s. deviation of 0.0408 Å. In the crystal, molecules are linked into centrosymmetric dimers by a pair of N—H⋯O hydrogen bonds. The ethyl group is disordered over two positions in a ratio of 0.758 (6):0.242 (6).

In the title compound, C 13 H 13 NO 4 , the fused-ring system is nearly planar, with an r.m.s. deviation of 0.0408 Å . In the crystal, molecules are linked into centrosymmetric dimers by a pair of N-HÁ Á ÁO hydrogen bonds. The ethyl group is disordered over two positions in a ratio of 0.758 (6):0.242 (6).

Xing-Yao Li and Jin-Long Wu Comment
Derivatives of isoquinoline-1,3(2H,4H)-dione are important compounds in pharmaceutical chemistry and have great research values, such as inhibitors of the cyclic-dependent kinase 4 (CDK4) (Tsou et al., 2008(Tsou et al., , 2009Lu et al.., 2010); inhibitors of HIV-1 integrase (Billamboz et al., 2011). In our research of synthesis of cyclonitrones, we have obtained the title compound as a minor product from ethyl 2-(2-(1,3-dioxolan-2-yl)phenyl)-2-cyanopropanoate hydrolysed by hydrogen peroxide. The structure of the title compound has been characterized by spectroscopic methods and further confirmation by X-ray analysis. We report here its crystal structure. In the molecule of the title compound ( Fig. 1), there is one benzene ring fused by carbonyl amide closing six-membered heterocyclic ring, the two rings are almost coplanar with only 1.02 (10)° dihedral angle. One sterogenic center but the crystallizes as a racemate as indicated by the centrosymmetric space group. In the crystal structure, molecules are linked by two N-H···O hydrogen bonds into dimers that are located on centres of inversion.

Refinement
The H atoms were placed in calculated positions with C-H = 0.93-0.97 Å, N-H = 0.86 Å and included in the refinement as riding their carrier atoms with U iso (H)=1.2U eq (C,N).

Ethyl 4-methyl-1,3-dioxo-1,2,3,4-tetrahydroisoquinoline-4-carboxylate
Crystal data C 13 H 13 NO 4 M r = 247.24 Triclinic, P1 Hall symbol: -P 1 a = 6.4585 (9) Å b = 8.1999 (7) Å c = 12.5763 (11) Å α = 78.876 (7) 169.1, 163.6, 140.1, 134.8, 128.9, 128.6, 125.9, 123.5, 62.6, 55.0, 25.1, 13.7 ppm. 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 > 2sigma(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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ. (