ENANTIOSELECTIVE HYDROGENATION OF OLEFINS WITH HOMOGENEOUS ZIEGLER-NATTA CATALYSTS

Styrene, 2-methyl-1-pentene, 2-phenyl-1-butene, and cis- and trans-2-hexene have been hydrogenated in the presence of catalysts derived from [Al(CH3)-O]nand (-)-[ethylenebis(4,5,6,7-tetrahydro-1(R)-indenyl)]zirconium derivatives. α-Olefins are readily polymerized with this catalytic system; in the presence of hydrogen, hydrogenated monomers can be obtained depending on the hydrogen pressure. Terminal olefins substituted in the 2- or 3-positions and internal olefins are not polymerized but undergo hydrogenation. Styrene is hydrogenated at 12 turnovers/min at 20 atm of H2at 25 °C with this catalytic system. The catalytic deuteriation of styrene with [(-)-(EBTHI)ZrX, X = (R)-1,1'-bi-2-naphtholate] 2 yields (-)-(R)-1,2-dideuterioethylbenzene in 93% yield with an optical purity of 65%, indicating that the (Re) enantioface of styrene is deuterated preferentially. This is the opposite enantioface selectivity as observed in propylene oligomerization with the same catalytic system. In the presence of 2, 2-phenyl-1-butene is hydrogenated to give (-)-(R)-2-phenylbutane in 95% yield with an optical purity of 36%. These results are discussed on the basis of a simple stereochemical model for the transition state of the olefin insertion step. © 1990, American Chemical Society. All rights reserved.