Asymmetrische Michael-Additionen. Praktisch vollstaendig diastereo- und enantioselective Alkylierungen des Enamins aus Cyclohexanon und Prolinylmethylaether durch ω-Nitrostyrole zu u-2-(1'-Aryl-2'-nitroaethyl)cyclohexanonen

Article abstract of DOI:10.1002/hlca.19820650537

When the enamine (S)-N-(1'-cyclohexenyl)-2-methoxymethyl-pyrrolidine is added to 2-aryl-1-nitroethylenes, only one of the four possible enantiomerically pure diastereomers is formed.Hydrolysis of the crude primary products furnishes α-alkylated cyclohexanones of >90percent e.e. (3, Scheme 3).Their (2S,1'R)-configuration was deduced by chemical correlation with 1-cyclohexyl-1-phenyl-ethane and from an X-ray crystal structure analysis of (-)-(2R,3S,6'R,1''S)-3-methyl-N-<6'-(2''-nitro-1''-phenylethyl)-1'-cyclohexenyl>-2-phenylmorpholine (11a, Scheme 5 and Fig. 2). - The relative topicity of reactant approach with the prolinol derivative (see II) is specified as 1k,ul-1,4.The steric course and the mechanism of the reaction are discussed.