2-[1′-(Benzyloxy)spiro[indane-1,2′-pyrrolidine]-5′-yl]acetonitrile

In the title compound, C21H22N2O, the planes of the two six-membered rings make a dihedral angle of 89.51 (7)°. The pyrrolidine ring has a puckering amplitude q 2 = 0.418 (3) and a pseudo-rotation phase angle ϕ2 = −166.8 (5), adopting a twist conformation (T). The other five-membered ring has a puckering amplitude q 2 = 0.247 (2) and a pseudo-rotation phase angle ϕ2 = −173.7 (5), adopting an envelope conformation with the CH2 atom adjacent to the C atom common with the pyrrolidine ring as the flap. In the crystal, molecules are linked via C—H⋯N, enclosing R 2 2(20) rings, forming chains propagating along [100]. The acetonitrile group is disordered over two positions and was refined with a fixed occupancy ratio of 0.56:0.44.

In the title compound, C 21 H 22 N 2 O, the planes of the two sixmembered rings make a dihedral angle of 89.51 (7) . The pyrrolidine ring has a puckering amplitude q 2 = 0.418 (3) and a pseudo-rotation phase angle ' 2 = À166.8 (5), adopting a twist conformation (T). The other five-membered ring has a puckering amplitude q 2 = 0.247 (2) and a pseudo-rotation phase angle ' 2 = À173.7 (5), adopting an envelope conformation with the CH 2 atom adjacent to the C atom common with the pyrrolidine ring as the flap. In the crystal, molecules are linked via C-HÁ Á ÁN, enclosing R 2 2 (20) rings, forming chains propagating along [100]. The acetonitrile group is disordered over two positions and was refined with a fixed occupancy ratio of 0.56:0.44.
The title compound crystallizes in the monoclinic space group P2 1 /c. The two phenyl rings are oriented to each other with a dihedral angle of 89.51 (7)°. Analysis of torsion angles, and least-square plane calculation, indicate that pyrrolidine ring shows a puckering amplitude q 2 = 0.418 (3) and pseudo-rotation phase angle φ 2 = -166.8 (5) adopting a twist conformation T with the N atom above the mean plane of the ring. In the same way the other five member ring shows a puckering amplitude q 2 = 0.247 (2) and pseudo-rotation phase angle φ 2 = -173.7 (5) adopting an envelope conformation E with the atom C9 below the mean plane of the ring (Cremer & Pople, 1975). The N-O bond length is close to the mean value [1.463 (12) Å] reported in the literature (Allen et al., 1987) and the torsion angle formed by the atoms [N1-O1-C15-C16] which links the pyrrolidine and phenyl rings is 179.41 (13)°. The crystal packing reveals that the molecules are linked through a network of weak C-H···N and C-H···O intermolecular interactions (see Table 1, Nardelli, 1995). The C21 atom in the molecule at (x,y,z) donates a proton to N2a y N2b atoms in the molecule at (-x+2,-y+2,-z+1), forming as a result of these interactions R 2 2 (20) rings (Etter, 1990). These rings are in turn linked by a weak C-H···O interaction. Indeed, the C23 atom in the molecule at (x,y,z) donates a proton to O1 atom of the molecule at (-x+1,-y+2,-z+1) forming layers parallel to (001)

Experimental
The reagents and solvents for the synthesis were obtained from the Aldrich Chemical Co., and were used without additional purification. A solution of 6-(benzyloxyimino)-8-(2-iodophenyl)oct-2-enenitrile (II) (129 mg, 0.29 mmol), 2,2′azobisisobutyronitrile (AIBN, 14 mg, 0.09 mmol) and tributyltin hydride (n-Bu 3 SnH, 0.09 ml, 0.35 mmol) in cyclohexane (Cy, 13 mL) was degassed for 1 h by bubbling dry argon, and subsequently stirred at 353 K for 7 h. After cooling to room temperature the solvent was removed under reduced pressure and the crude product treated with a mixture of 20% KF aqueous solution (2 mL) and ethyl acetate (2 mL), stirring overnight. The organic layer was separated, dried with anhydrous Na 2 SO 4 and filtered over silica gel. The purification was carried out by flash column chromatography with 60-95% benzene/hexane (gradient 5%) to afford a mixture of two diastereomers IIIa and IIIb (59 mg, 65%) as yellow oil.

Refinement
The H-atoms were positioned geometrically [C-H= 0.93 Å for aromatic and C-H= 0.97 Å for methylene, and with U iso (H) (1.2 and 1.5 times U eq of the parent atom respectively]. The H12 atom was found in difference Fourier maps an its coordinates were refined freely.

Figure 2
Part of the crystal structure of (IIIa), forming layers in the ab plane. Symmetry code: (i) -x+2,-y+2,-z+1; (ii) -x+1,-y+2,-  Reaction scheme. 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 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. (