Highly Stereoselective Isomerization of Monosubstituted 1-Alkenes to (E)-2-Alkenes by Catalysis of (C5Me5)2TiCl2/NaC10H8

The catalyst systems which consist of MCl2(C5R5)2(M=Ti, Zr; R=H, CH3)/NaC10H8, i-C3H7MgBr, n-C4H9Li or LiAlH4 in 1 : 2 ratio were highly effective for the stereoselective isomerization of monosubstituted 1-alkenes to (E)-2-alkenes. Unconjugated dienes were converted to (E)- or (E,E)-dienes. The catalysis of (C5Me5)TiCl2/NaC10H8 was extremely high and resulted in the complete isomerization of 1-alkenes in >99% stereoselectivity within a short period. The use of the bulky C5Me5 ligand is essential to find out the excellent stereoselectivity. Systems, (C5H5)2TiCl2/NaC10H8 and (C5H5)2TiCl2/i-C3H7MgBr showed less selectivity and the catalysis of the corresponding zirconium systems was very poor irrespective of the reducing agents and substrates.