Chiral bis(dihydrooxazolyl)pyridineruthenium complexes of trans-cycloodeneand trans-cycloheptene

Asymmetric reaction of an excess of trans-cyclooctene (1) with chiral bis(d ihydrooxazolyl)pyridineruthenium (pybox-ip, 3) complex selectively gives th e corresponding ruthenium complex 4R, [RuCl2(pybox-ip){(R)-trans-cycloocten e}], and (S)-trans-cyclooctene 2S. The X-ray crystal structure of complex 4 R shows a C25-C18-C19-C20 dihedral angle of 125 degrees with a C18-C19 bond length of 1.41 Angstrom. Complex 4R can also be obtained by UV irradiation of a solution of cis-cyclooctene and [RuCl2-(pybox-ip)(C2H4)] (8) in THF i n the presence of a photosensitizer. Even in the absence of the photosensit izer, 4R is produced by irradiation in the presence of cis-cyclooctene. The photoreaction has been applied to cis-cycloheptene to give a 1:1 mixture o f the diastereomeric complexes of [Ru(pybox-ip)-{trans-cycloheptene}].