Crystal structure of 2-methylamino-3-nitro-4-p-tolylpyrano[3,2-c]chromen-5(4H)-one

In the racemic title compound, C20H16N2O5, the pyran ring adopts a shallow envelope conformation, with the stereogenic C atom displaced from the other atoms by 0.273 (2) Å. The dihedral angle between the fused-ring system and the pendant p-tolyl group is 87.62 (7)°. The molecular conformation is consolidated by an intramolecular N—H⋯O hydrogen bond, which generates an S(6) ring. In the crystal, molecules are linked by C—H⋯O interactions, resulting in [010] chains.

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S2. Experimental
A solution of 4-methylbenzaldehyde (1.0 mmol), 4-hydroxycoumarin (1.0 mmol), NMSM (1.0 mmol), and piperidine (0.2 equiv) in EtOH (2 ml) was stirred for the three hours. After reaction was complete as indicated by TLC, the product was filtered and washed with EtOH (2 ml) to remove the excess base and other impurities. Finally, the product was recrystallized from EtOH to yield colourless blocks of the title compound.

S3. Refinement
N and C-bound H atoms were positioned geometrically (C-H = 0.93-0.98 Å) and allowed to ride on their parent atoms, with U iso (H) = 1.5U eq (C) for methyl H atoms and 1.2U eq (C) for all other H atoms.
supporting information

Figure 1
The molecular structure of the title molecule, with atom displacement ellipsoids drawn at the 30% probability level. The intramolecular N-H···O hydrogen bond, which generates an S(6) ring motif, is shown as a dashed line.

Figure 2
The crystal packing of the title compound, viewed along the b axis, showing C9-H9C···O4 hydrogen bonds producing chains parallel to the 101 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.