{(1R,3S)-2-Benzyl-6,7-dimethoxy-1-phenyl-1,2,3,4-tetrahydroisoquinolin-3-yl}diphenylmethanol

In the title compound, C37H35NO3, a precursor to novel chiral catalysts, the N-containing six-membered ring assumes a half-chair conformation. Intermolecular C—H⋯O hydrogen bonds link the molecules in the crystal structure.

In the title compound, C 37 H 35 NO 3 , a precursor to novel chiral catalysts, the N-containing six-membered ring assumes a halfchair conformation. Intermolecular C-HÁ Á ÁO hydrogen bonds link the molecules in the crystal structure. H atoms treated by a mixture of independent and constrained refinement Á max = 0.14 e Å À3 Á min = À0.12 e Å À3 Table 1 Hydrogen-bond geometry (Å , ). Symmetry code: (i) x; y; z À 1.

Comment
The title compound (2, Fig. 3) is a precursor in the synthesis of novel chiral ligands involving a tetrahydroisoquinoline backbone. Recently, we have reported the application of these ligands as useful catalysts for transfer hydrogenation reactions (Chakka et al., 2010).
Compound 2 contains four phenyl rings and the absolute stereochemistry was confirmed to be R,S at C1 and C9 positions as shown in Fig. 1, respectively (Aubry et al., 2006). The crystal packing is stabilized by intermolecular C-H···O hydrogen bonds. The H atom of methanol does not form hydrogen bonds (Table 1 & Fig. 2). According to the Cambridge structural data base this is the first tetrahydroisoquinoline derivative with diaryl substitution at the C10 position. The structure displays a gauche or sc (synclinal) conformation around the O3-C10-C9-N1 bond with the OH group almost over the piperidine ring with a torsion angle of -77.0 (2)°. Due to the lack of analogous structures this observation was compared to proline diaryl alcohols (Seebach et al., 2008) which display a similar conformation around the exocyclic C9-C10 bond. Given the success of proline diaryl alcohols as a chiral catalyst (Diner et al., 2008) this comparison is particularly useful for catalysts bearing a tetrahydroisoquinoline framework as this feature could have a significant effect on the stereocontrol of the catalyst.
We recently reported a crystal structure of a similar molecule to the title compound (Naicker et al., 2009) which has an ester moiety at the C10 position and the N-containing six membered ring assumes a half boat conformation. The N-containing six membered ring in the title compound exists in a half chair conformation (see Fig. 1). A possible reason for this difference in conformation could be the introduction of large phenyl ring substitiuents at the C10 position. The efficiency of these tetrahydroisoquinoline catalysts is currently being tested in our laboratory.
Light yellow crystals suitable for X-ray diffraction were obtained by slow evaporation of 2 in dichloromethane at room temperature.

Special details
Experimental. Half sphere of data collected using SAINT strategy (Bruker, 2006). Crystal to detector distance = 50 mm; combination of φ and ω scans of 0.5°, 70 s per °, 2 iterations.
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 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.