Abstract
The (cymene)ruthenium halfsandwich complexes K1 and K2 with chiral pyrroleoxazoline ligands were synthesized and characterized. The complexes form diastereomers, which only differ in the metal configuration. Complex K1 crystallized as the pure diastereomer S-Ru,S-C4.P-C5. In solution epimerization S-Ru,S-C4,R-C5 reversible arrow R-Ru,S-C4,P-C5 occurred via change of the configuration at the ...
Abstract
The (cymene)ruthenium halfsandwich complexes K1 and K2 with chiral pyrroleoxazoline ligands were synthesized and characterized. The complexes form diastereomers, which only differ in the metal configuration. Complex K1 crystallized as the pure diastereomer S-Ru,S-C4.P-C5. In solution epimerization S-Ru,S-C4,R-C5 reversible arrow R-Ru,S-C4,P-C5 occurred via change of the configuration at the ruthenium atom. The half-life for the first-order reaction at 0.4 degreesC in CD2Cl2 was 50.6 min. Thus, the two diastereomers equilibrate at room temperature. The equilibrium mixtures of K1 and K2 were used as catalysts for the transfer hydrogenation of acetophenone and for the Diels-Alder reaction of cyclopentadiene with methacrolein. Enantiomeric excesses of up to 60% ee were achieved.
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