ABSTRACT
Enantio- and diastereoselective hydrogenation of ß-keto-γ-lactams with a ruthenium-BINAP catalyst, involving dynamic kinetic resolution, has been employed to provide a general, asymmetric approach to ß-hydroxy-γ-lactams, a structural motif common to several bioactive compounds. Full conversion to the desired ß-hydroxy-γ-lactams was achieved with high diastereoselectivity (up to >98% de) by addition of catalytic HCl and LiCl, while ß-branching of the ketone substituent demonstrated a pronounced effect on the modest to excellent enantioselectivity (up to 97% ee) obtained.
ABSTRACT
The first examples of asymmetric copper-catalysed intramolecular C-H insertion reactions of 2-sulfonyl-2-diazoacetamides are described; trans γ-lactams with up to 82% ee are achieved with the CuCl2-bisoxazoline-NaBARF catalyst system. The reactions generally display high efficiency and high trans selectivity, and also a strong regiochemical preference for insertion to lead to the formation of 5-membered rings over 4-membered rings. In cases where there are competing C-H insertion pathways available, to form sulfolanes or thiopyrans, only the insertion into the amide chain to form γ-lactams is observed. With phenylsulfonyl derivatives, a minor competing C-H insertion pathway leading to ß-lactams is seen; interestingly, changing the identity of the copper ligand changes the product ratio of ß/γ-lactams. The copper catalysed reactions compare favorably in terms of efficiency and enantioselectivity to the corresponding reactions catalysed by commercially available chiral rhodium catalysts.
