α‘-Hydroxy Enones as Achiral Templates for Lewis Acid-Catalyzed Enantioselective Diels−Alder Reactions
作者:Claudio Palomo、Mikel Oiarbide、Jesús M. García、Alberto González、Elena Arceo
DOI:10.1021/ja0368002
日期:2003.11.1
alpha'-Hydroxy enones react with dienes in the presence of (S,S)-[Cu(tBu-box)](OTf)2 or (S,S)-[Cu(tBu-box)](SbF6)2 (2 to 10 mol %) to afford the corresponding Diels-Alder adducts in high yield and selectivity. Isomeric ratios (regioselectivity, endo/exo or cis/trans) of up to >99:1 and ee values of up to >99% are obtained. Significantly, difficult dienes such as isoprene, 2,3-dimethyl butadiene and piperylene behave satisfactorily. Subsequent oxidative cleavage of the ketol in the resulting cycloadducts by treatment with cerium ammonium nitrate (CAN) yields the corresponding enantiopure carboxylic acids. Alternatively, carbonyl addition and subsequent diol cleavage with CAN produces the corresponding ketone adducts.
Catalytic Enantioselective Conjugate Addition of Carbamates
作者:Claudio Palomo、Mikel Oiarbide、Rajkumar Halder、Michael Kelso、Enrique Gómez-Bengoa、Jesús M. García
DOI:10.1021/ja047004e
日期:2004.8.1
Catalytic, asymmetric conjugate addition of carbamates to enoyl systems has been realized for the first time, providing a two-step access to virtually enantiopure N-protected beta-amino acids.
Lewis Acid Catalyzed Asymmetric Cycloadditions of Nitrones: α′-Hydroxy Enones as Efficient Reaction Partners
作者:Claudio Palomo、Mikel Oiarbide、Elena Arceo、Jesús M. García、Rosa López、Alberto González、Anthony Linden