1′-Benzylspiro[chromene-2,4′-piperidine]-4-carbonitrile

In the title compound, C21H20N2O, the piperidine ring adopts a chair conformation while the pyran ring adopts a screw-boat conformation. The piperidine ring forms dihedral angles of 65.75 (3) and 67.79 (5)° with the chroman and methyl-substituted benzene rings, respectively. The crystal structure features weak C—H⋯π and π–π [centroid–centroid distance = 3.8098 (8) Å] interactions.

In the title compound, C 21 H 20 N 2 O, the piperidine ring adopts a chair conformation while the pyran ring adopts a screw-boat conformation. The piperidine ring forms dihedral angles of 65.75 (3) and 67.79 (5) with the chroman and methylsubstituted benzene rings, respectively. The crystal structure features weak C-HÁ Á Á and -[centroid-centroid distance = 3.8098 (8) Å ] interactions.
The crystal structure of the title compound demonstrates the importance of weak interactions in optimizing the molecular aggregation in crystals. With the lone acceptor oxygen O1 unavailable for participation in intermolecular interactions for sterical reasons, the weak C-H···π and π···π interactions assume significance. A C3-H3···Cg1 (1 -x, 1/2 + y, 1/2 -z), Cg1 being the centroid of the benzene ring defined by C15 -C20, having a distance of 2.95 Å and angle of 146°, generates chains running along the b axis. A Cg2··· Cg2 (-x + 1, y + 1/2, -z + 1/2) interaction, Cg2 being the centroid of the benzene ring defined by C2 -C7, observed between two benzene rings of the chroman. The corresponding ring-centroid separation is 3.8098 (8) Å, with an interplanar spacing of ca 3.51 Å and a ring offset of ca 1.48 Å. These interactions generate a π-stacked extended sheets running parallel to the [011] direction (Fig. 3).
The accurate description of the crystal structure of title compound is of interest due to the absence of conventional hydrogen bonding and thus gains importance in the context of crystal structure prediction. Precise single-crystal X-ray investigations on similar compounds might throw light on the delicate nature of intermolecular interactions.

Experimental
Trimethylsilylcyanide (1.2 mmol) was added to a mixture of 1′1′-benzyl-3, 4-dihydrospiro [1-benzopyran-2, 4′piperidine]-4-one (1.0 mmol) and catalytic amount of ZnI 2 in dichloromethane (10 vol), under a nitrogen atmosphere. The reaction mixture was stirred at 50°C for 6 h and then cooled to room temperature, dilute HCl (5 ml) was added and stirring continued for additional 2 h. The solution was extracted with ethylacetate (20 ml), dried over Na 2 SO 4 and evaporated to dryness. The crude product was dissolved in benzene (10 ml), to which tosic acid (0.1 mmol) had been added and the solution was heated to reflux for 2 h. After completion of the reaction as indicated by TLC, the reaction supplementary materials sup-2 Acta Cryst. (2012). E68, o2732 mixture was concentrated under reduced pressure. The residue was diluted with ethylacetate (20 ml), washed with bicarbonate solution (10 ml) dried and concentrated. The crude product was purified by column chromatography to provide the desired product as colorless solid. Crystals of the title compound were grown from its solution in ethanol by slow evaporation at room temperature.

Figure 1
The molecular structure of the title compound showing 50% probability displacement ellipsoids.   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.