COLL 193 |
| The asymmetric hydrogenation of alpha-ketoesters on cinchona-modified supported platinum particles is a prototype reaction in heterogeneous chiral catalysis. We will show that chemisorption-induced polarization leads to an aromatic-carbonyl H-bonding interaction between the aromatic anchor of the modifier and the coadsorbed substrate. By specifying that the aromatic C-H...O interaction is to the prochiral carbonyl, and that it is accompanied by a H-bonding interaction between the ester carbonyl and the quinuclidine function, we show that it is possible to rationalize essentially all of the catalysis literature for the Orito reaction in terms of a single molecular mechanism. The generality of the proposed mechanistic model is demonstrated by addressing data from the literature for a representative range of substrates, modifiers, solvents and metals. |
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Chirality and Enantioselectivity at Surfaces
2:00 PM-5:30 PM, Monday, 11 September 2006 Sir Francis Drake -- Windsor Room, Oral
Division of Colloid & Surface Chemistry |