Practical and highly enantioselective ring opening of cyclic meso-anhydrides mediated by cinchona alkaloids.
The cinchona alkaloid-mediated opening of prochiral cyclic anhydrides in the presence of methanol leading to optically active hemiesters is described. Very structurally diverse anhydrides are converted into their corresponding methyl monoesters, and either enantiomer can be obtained with up to 99% ee by using quinine or quinidine as directing additive. After the reaction, the alkaloids can be recovered almost quantitatively and reused without loss of enantioselectivity. Additionally, a catalytic protocol which permits the substoichiometric use of quinidine in the presence of easily accessible pentamethylpiperidine (pempidine) is presented.
Bolm
C
C
Institut für Organische Chemie der RWTH Aachen, Prof. -Pirlet-Strasse 1, D-52056 Aachen, Germany. carsten.bolm@oc.rwth-aachen.de
Schiffers
I
I
Dinter
C L
CL
Gerlach
A
A
D000812:Anhydrides / Q000737:chemistry*; D002384:Catalysis; D002930:Cinchona Alkaloids / Q000737:chemistry*; D003500:Cyclization; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D011802:Quinidine / Q000737:chemistry; D013237:Stereoisomerism
D000812:Anhydrides; D002930:Cinchona Alkaloids; D011802:Quinidine