Aminocyclopentadienyl Ruthenium Complexes as Racemization Catalysts for Dynamic Kinetic Resolution of Secondary Alcohols at Ambient Temperature
Citations Over TimeTop 10% of 2004 papers
Abstract
Aminocyclopentadienyl ruthenium complexes, which can be used as room-temperature racemization catalysts with lipases in the dynamic kinetic resolution (DKR) of secondary alcohols, were synthesized from cyclopenta-2,4-dienimines, Ru(3)(CO)(12), and CHCl(3): [2,3,4,5-Ph(4)(eta(5)-C(4)CNHR)]Ru(CO)(2)Cl (4: R = i-Pr; 5: R = n-Pr; 6: R = t-Bu), [2,5-Me(2)-3,4-Ph(2)(eta(5)-C(4)CNHR)]Ru(CO)(2)Cl (7: R = i-Pr; 8: R = Ph), and [2,3,4,5-Ph(4)(eta(5)-C(4)CNHAr)]Ru(CO)(2)Cl (9: Ar = p-NO(2)C(6)H(4); 10: Ar = p-ClC(6)H(4); 11: Ar = Ph; 12: Ar = p-OMeC(6)H(4); 13: Ar = p-NMe(2)C(6)H(4)). The tests in the racemization of (S)-4-phenyl-2-butanol showed that 7 is the most active catalyst, although the difference decreased in the DKR. Complex 4 was used in the DKR of various alcohols; at room temperature, not only simple alcohols but also functionalized ones such as allylic alcohols, alkynyl alcohols, diols, hydroxyl esters, and chlorohydrins were successfully transformed to chiral acetates. In mechanistic studies for the catalytic racemization, ruthenium hydride 14 appeared to be a key species. It was the major organometallic species in the racemization of (S)-1-phenylethanol with 4 and potassium tert-butoxide. In a separate experiment, (S)-1-phenylethanol was racemized catalytically by 14 in the presence of acetophenone.
Related Papers
- → Chemoenzymatic Dynamic Kinetic Resolution of Alcohols and Amines(2009)229 cited
- → Efficient ruthenium-catalyzed racemization of secondary alcohols: application to dynamic kinetic resolution(2002)88 cited
- → Photoactivated Racemization Catalyst for Dynamic Kinetic Resolution of Secondary Alcohols(2010)34 cited
- → Dynamic Kinetic Resolution of rac‐2‐Hydroxy‐1‐indanone by using a Heterogeneous Ru(OH)3/Al2O3 Racemization Catalyst and Lipase(2010)17 cited
- → (η5-Triphenylindenyl)Ru(CO)2Cl: A New Ruthenium Catalyst for the Highly Efficient Racemization of Chiral 1-Phenylethanol at Room Temperature(2006)1 cited