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Asymmetric Aza-Henry Reaction Under Phase Transfer Catalysis: An Experimental and Theoretical Study

2008; American Chemical Society; Volume: 130; Issue: 25 Linguagem: Inglês

10.1021/ja800253z

1943-2984

Enrique Gómez‐Bengoa, Anthony Linden, Rosa López, Idoia Múgica-Mendiola, Mikel Oiarbide, Claudio Palomo,

Organic and Inorganic Chemical Reactions

An efficient catalytic asymmetric aza-Henry reaction under phase transfer conditions is presented. The method is based on the reaction of the respective nitroalkane with α-amido sulfones effected by CsOH·H2O base in toluene as solvent and in the presence of cinchone-derived ammonium catalysts. This direct aza-Henry reaction presents as interesting features its validity for both nonenolizable and enolizable aldehyde-derived azomethines and the tolerance of nitroalkanes, other than nitromethane, for the production of β-nitroamines. The synthetic value of the methodology described is demonstrated by providing (a) a direct route for the asymmetric synthesis of differently substituted 1,2-diamines and (b) a new asymmetric synthesis of γ-amino α,β-unsaturated esters through a catalytic, highly enantioselective formal addition of functionalized alkenyl groups to azomethines. Finally, a preferred TS that nicely fits the observed enantioselectivity has been identified. Most remarkable, an unusual hydrogen bond pattern for the catalyst-nitrocompound-imine complex is predicted, where the catalyst OH group interacts with the NO2 group of the nitrocompound.