Nitroalkane electron acceptor

Mechanistically related are the reactions of nitroalkane anions with strongly electron-deficient olefins21"25. Following Michael addition, a cycloalkylation, under nitrite expulsion, produces cyclopropane derivatives with acceptor groups. At least in certain examples, the configuration of the precursor olefin is reflected in the stereochemistry of the resulting cyclopropane22. 

Carbon-carbon bond forming reactions between carbanionic nucleophiles like enolates or deprotonated nitroalkanes and electron deficient alkenes and alkynes belong to the oldest and most versatile transformations known today (225-229). Moreover, stereoselective variants have proven to possess an enormous potential in the syntheses of complex molecules as already exemplified in Sect. 2.4. Whereas the applications depicted in this previous section utilized nucleophiles activated by enamine formation with a chiral secondary amine catalyst to achieve these highly selective C-C bond formations, the present discussirai will focus on the addition of carbon nucleophiles to iminium-activated Michael acceptors. Herein traditional Michael additions using e.g. enolate nucleophiles will be described whereas the use of aromatic Michael donors with iminium-activated acceptors in Friedel-Crafts type reactions will be discussed separately subsequently. 

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