Sulfoximines – Catalysis
As early as in the seventies β-hydroxysulfoximines have been reacted with borane to realize asymmetric reductions of carbonyl compounds. Later sulfoximines have been applied as ligands for metals like zinc, copper and nickel . (Review)
We used C-phosphanylated sulfoximines (see x-ray to the right and red structure below) derived from as ligands fpr palladium in asymmetric allylic substitution reactions. Thereby, we achieved enantiomeric excesses up to 95% ee ( enantiomerically pure sulfonimidates 2006, 17, 500-503). Tetrahedron-Asymmetry
As a byproduct of the synthesis of the methyl sulfoximine 2 from the cyclic sulfonimidate 1 we always observed changing amounts of the bissulfoximine 3. By variation of the reaction conditions it was possible to make the formation of this interesting C2-symmetric compound the major process.
After twofold O-silylation of 3 it is possible to obtain a copper complex, the bisstriflate of which was amenable to x-ray structural analysis. This complex catalyses the 1,4-addition of diethyl zinc to enones (). Moreover, we successfully phosphanylated the side chains and prepared heterobimetal complexes with copper and rhodium thereof (unpublished results). DOI: 10.1002/adsc.200404164
Geminal bissulfoximines like 3 were unknown before our work. This may be a consequence of the problematic double imination of the underlying and well known bissulfoxide ( (opens in new tab) ). In order to explore the synthetic potential of this class of compounds as chiral, C2-symmetric ligands best, we developed an entry to the so-called “free” bissulfoximine 5. This was achieved by a zinc mediated β-elimination of the dibromo derivative 4 ( Reggelin, Ph.D. 1989). DOI: 10.1055/s-0031-1290759