Two Related Benzylcamphor Dimers

The crystal structures of two related dimeric 3-benzyl-camphors, namely, (1R,3R,4R,1'R,3'R,4'R)-3,3'-[(1R,2R)-1,2-diphenylethylene]bis(1,7,7-trimethylbicyclo[2.2.1]- heptan-2-one), (1), and (1R,3R,4R, 1'R,3'S,4'R)-3,3'- [(1R,2S)-1,2-diphenylethylene] bis(1,7,7-trimethylbicyclo-[2.2.1]heptan-2-one), (2), both C34H42O2, are reported. Compound (1) possesses C-2 molecular symmetry; it adopts a conformation in the crystal in which the two phenyl rings are gauche with respect to one another and anti to the C3-C4 bond (terpene numbering) of the camphor ring system. Compound (2) lacks a molecular C-2 axis of symmetry; it adopts a conformation in the crystal where the two phenyl rings are anti with respect to one another, and in which one phenyl ring is partially in the endo cavity of the camphor ring system. In both compounds, C3 of both camphor ring systems (terpene numbering) is distorted to trigonal pyramidal from tetrahedral; the C-C-C bond angles about C3 in both camphor rings are considerably expanded from idealized tetrahedral values and the dihedral angle between the benzyl C atom and the carbonyl O atom is reduced from the idealized value of 60 degrees to less than 48 degrees.