Thursday, August 23, 2007

Computer aid Rh(II) catalyst design and synthesis

before I enter the project, the first generation cat. Rh2Ln2 was already made successfully, can catalyze C-H insertion, high ee but very low yield. We believe the very big and interconnected ligands blocked the active site of the Rh metal and were the reason for the low reactivity.

In the 2nd generation cat. Rh2T2, the ligand was smaller and interconnected by less number of carbons than the first generation. The only problem is the synthesis of the ligand was not successful.

So we did a little change to the ligand, which made the synthesis easier. The ligand was synthesized by diels-alder reaction of Evan's chiral auxiliary. But the reaction between Rh2(TFA)4 and the ligand is not successful. polymer like material was resulted, poor solubility in almost all organic solvents. Poor reactivity toward C-H insertion.

The reason I think is that the two carboxyl group of the ligand connected with two molecular of Rh2 instead of one Rh2. So you get a big molecular, a polymer.

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