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Synfacts 2007(7): 0736-0736
DOI: 10.1055/s-2007-968611
DOI: 10.1055/s-2007-968611
Metal-Catalyzed Asymmetric Synthesis and Stereoselective Reactions
© Georg Thieme Verlag Stuttgart · New York
Asymmetric Diels-Alder Reaction with 2-Alkenoyl Pyridine N-Oxides
S. Barroso, G. Blay, J. R. Pedro*
Universitat de ValÈncia, Spain
Further Information
Publication History
Publication Date:
22 June 2007 (online)
Significance
Many chiral catalysts have been developed for enantioselective Diels-Alder reactions, most of them involving Cu(II) complexes. However, with pyridine alkenoyl substrates, the Cu-BOX system was restricted to cyclopentadiene as effective diene partner. The use of the pyridine N-oxide increased the reactivity of the dienophile to allow a variety of less reactive acyclic dienes to react. It also greatly increased the selectivity, as the non-oxidized pyridine gave an endo/exo ratio of 86:14 with 19% ee for the endo-adduct 3, as opposed to the N-oxide, which gave 97.5:2.5 and 96% ee.