5-Benzyl-5H-pyrido[3,2-b]indole

The title compound, C18H14N2, was prepared by twofold Pd-catalyzed arylamination of a cyclic pyrido–benzo–iodolium salt. In the crystal, two molecules of 9-benzyl-δ-carboline form centrosymmetrical dimers with distances of 3.651 (2) Å between the centroids of the pyridine rings and 3.961 (2) Å between the centroids of the pyrrole and pyridine rings. The phenyl rings point to the other molecule in the dimer and the carboline core is essentially planar [maximum deviation of 0.027 (2) Å].

The title compound, C 18 H 14 N 2 , was prepared by twofold Pdcatalyzed arylamination of a cyclic pyrido-benzo-iodolium salt. In the crystal, two molecules of 9-benzyl--carboline form centrosymmetrical dimers with distances of 3.651 (2) Å between the centroids of the pyridine rings and 3.961 (2) Å between the centroids of the pyrrole and pyridine rings. The phenyl rings point to the other molecule in the dimer and the carboline core is essentially planar [maximum deviation of 0.027 (2) Å ].    (2011), but this approach is not suitable for the synthesis of the δ-isomers. These can now be prepared in a twofold Pd-catalyzed arylation of primary amines with cyclic pyrido-benzo iodolium salts. This unique 9-substituted δ-carboline crystallizes in form of centrosymmetrical dimers. The phenyl group, pointing in the direction of the second molecule, is nearly orthogonal to the essentially planar carboline core (maximal deviations of 0.027 (2) Å from the least square plane).

Experimental
Short distances of the centroid of a pyridine ring of one molecule to the centroid of the pyridine of its counterpart of 3.65 Å and to the pyrrole centroid of 3.96 Å indicate a π-π interaction between the heterocycles.

Refinement
Hydrogen atoms attached to carbons were placed at calculated positions with C-H = 0.95 Å (aromatic) or 0.98-0.99 Å (sp 3 C-atom). All H atoms were refined in the riding-model approximation with isotropic displacement parameters (set at 1.2-1.5 times of the U eq of the parent atom).
supplementary materials sup-2 Figures Fig. 1. View of compound I. Displacement ellipsoids are drawn at the 50% probability level.

Special details
Experimental .  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.