Highly enantioselective iridium-catalyzed hydrogenation of α,β-unsaturated esters
α,β-Unsaturated esters have been employed as substrates in iridium-catalyzed asymmetric hydrogenation. Full conversions and good to excellent enantioselectivities (up to 99 % ee) were obtained for a broad range of substrates with both aromatic- and aliphatic substituents on the prochiral carbon. The hydrogenated products are highly useful as building blocks in the synthesis of a variety of natural products and pharmaceuticals. Asymmetric hydrogenation: A variety of α,β-unsaturated esters were hydrogenated with high enantioselectivities (see scheme). The hydrogenated products have been used in synthetic transformations as well as in formal total syntheses. Copyright
Li, Jia-Qi,Quan, Xu,Andersson, Pher G.
p. 10609 - 10616
(2012/11/07)
A KINETIC STUDY ON ASYMMETRIC TRANSFER HYDROGENATION OF UNSATURATED ACIDS AND ESTERS BY ALCOHOLS WITH BINUCLEAR RUTHENIUM(II) CHIRAL DIPHOSPHINE COMPLEXES
Kinetic investigation of the 3> catalysed transfer hydrogenation of unsaturated acids and esters by alcohols indicated that the catalytically active > complex generated from the 3> > + 2> reaction afforded chiral hydrogenated products via the reaction of a hydrogen acceptor-> (hydrogen donor) complex and of a hydrogen donor-> (hydrogen acceptor) complex. 31P N.m.r. analysis of 3> in solution also suggested the possibility of 3> formation from 3>.The reaction mechanism is also discussed on the basis of isotope effects observed in the 3> catalysed reaction between deuteriated benzyl alcohols and unsaturated species.