Chiral nitrogen-stabilized Fischer carbene complexes: an efficient tool in the stereocontrolled elaboration of additional stereogenic centers
The elaboration of the organic ligand of amino and hydrazino carbene complexes of the Fischer type through the reactions of their anions with electrophiles is a useful tool for achieving the stereoselective formation of new carbon-carbon bonds. Anions of chiral carbene complexes substituted with a C2 symmetry amine give stereoselective 1,4-Michael additions to nitroolefins, thus achieving a new entry to b-aryl-g-aminobutyric acid derivatives, which are biologically important molecules. Moreover, two new and complementary protocols for the synthesis of alkyl hydrazino carbene complexes have been developed and the first reactions of their conjugated bases with alkyl halides and aldehydes are reported.