Ruthenium(II)-promoted site-selective intramolecular diels-alder reactions

Article abstract of DOI:10.1021/ic00321a019

The complex trans,trans,trans-dichlorodicarbonylbis(1-phenyl-3,4-dimethylphosphole) ruthenium(II) (1) undergoes intramolecular Diels-Alder [4 + 2] cycloadditions with vinyldiphenylphosphine, divinylphenylphosphine, vinyldiethylphosphine, phenyl vinyl sulfoxide, and N,N-dimethylacrylamide in dichloromethane at room temperature stereoselectivity in high yield to produce single diastereomers of mer-trans-dichlorocarbonyl-(1-phenyl-3,4-dimethylphosphole[2-(diphenylphosphino) -5,6-dimethyl-7-phenyl-7-phosphabicyclo[2.2.1]hept-5-ene]ruthenium(II) (2), mer-trans-dichlorocarbonyl(1-phenyl-3,4-dimethylphosphole)[2-(phenyl- vinylphosphino)-5,6-dimethyl-7-phenyl-7-phosphabicyclo[2.2.1]hept-5-ene] ruthenium(II) (3), mer-trans-dichlorocarbonyl(1-phenyl-3,4-dimethylphosphole)[2-(diethylphosphino)- 5,6-dimethyl-7-phenyl-7-phosphabicyclo[2.2.1]hept-5-ene]ruthenium(II) (4), mer-trans-dichlorocarbonyl(1-phenyl-3,4-dimethylphosphole)[2-(phenylsulfinyl)-5, 6-dimethyl-7-phenyl-7-phosphabicyclo[2.2.1]-hept-5-ene]ruthenium(II) (5), and mer-trans-dichlorocarbonyl(1-phenyl-3,4-dimethylphosphole)[2-(dimethylamino) carbonyl)-5,6-dimethyl-7-phenyl-7-phosphabicyclo[2.2.1]hept-5-ene]ruthenium(II) (6), respectively. In like manner, reactions of trans,-trans,trans-dichlorodicarbonylbis(vinyldiphenylphosphine)ruthenium(II) (7) with 1-phenyl-3,4-dimethylphosphole produces mer-trans-dichlorocarbonyl(vinyldiphenylphosphine)[2-(diphenylphosphino)-5,6- dimethyl-7-phenyl-7-phosphabicyclo[2.2.1]-hept-5-ene]ruthenium(II) (8). All these compounds contain conformationally rigid, chiral bidentate ligands. They have been characterized by elemental analysis, physical properites, cyclic voltammetry, infrared spectroscopy, and ¹H ¹³C{¹H}, ³¹P{¹H}, ¹H/¹³C HETCOR, and ¹H/¹H COSY nuclear magnetic resonance spectroscopy. The structures of 6 and 8 were confirmed by X-ray crystallography at -100°C. Both crystallize in the monoclinic space group P2₁/n in unit cells of the following dimensions: 6, a = 21.555 (6) A?, b = 10.794 (3) A?, c = 26.743 (8) A?, β = 91.91 (2)°, ρ(calcd) = 1.443 g cm^-3, Z = 8; 8, a = 10.173 (3) A?, b = 20.908 (6) A?, c = 17.136 (4) A?, β = 98.31 (2)°, ρ(calcd) = 1.485 g cm^-3, Z = 4. Refinements converged to R = 0.045 and R = 0.030 with 4192 and 3949 independent reflections, respectively. Some of these new complexes were tested as catalysts for the homogeneous hydrogenation of 1-hexene and found to be relatively poor catalysts.