rac-(2R,3S)-2-Phenyl-3-(3-phenyl-1,2,3,4-tetra-hydro-quinoxalin-2-yl)quinoxaline

The title compound, C(28)H(22)N(4), is the unexpected by-product of the reaction of 2-hydroxy-acetophenone and 1,2-diamino-benzene under iodine catalysis, during which a carbon-carbon σ-bond between two quinoxaline units was formed. Although a fully oxidized title compound should sterically be possible, only one quinoxaline ring is fully oxidized while the second ring remains in the reduced form. As expected, the tetra-hydro-quinoxaline unit is not planar; it adopts a sofa conformation, whereby the atom joining the two heterocyclic systems lies out of the plane of the other atoms. The quinoxaline ring system makes a dihedral angle of 53.61 (4)° with its phenyl ring substituent. The crystal packing is determined by pairs of N-H⋯N, N-H⋯π and weak C-H⋯N hydrogen bonds, forming a chain parallel to the a axis.