Diastereoselective synthesis of ferrocenyl sulfoximines with planar and central chirality

The capability of the sulfonimidoyl moiety to serve as ortho-directing group for the diastereoselective lithiation of enantiopure ferrocenylsulfoximines is demonstrated. (S)-N-p-Tolylsulfonyl-S-ferrocenyl-S-tert-butylsulfoximine showed excellent diastereoselectivity concerning planar chirality of the products obtained after quenching of the lithium species with several electrophiles. Various electrophiles (MeI, Me2S2, Me3SiCl, p-anisaldehyde, acetone, n-Bu3SnCl, I-2) were introduced in yields from 36 to 78%. Only up to 10% of product substituted at both the cyclopentadienyl ring and the phenyl group of the tosyl moiety was isolated as byproduct. The relative configuration of the products was determined by chemical correlation and X-ray crystallographic analysis of(S,R-p)-N-p-tolylsulfonyl-S-tert-butyl-S-(2-iodoferrocenyl)sulfoximine. Taking into account the structure of the starting material, the ortho-directing effect can be ascribed to the oxygen atom of the sulfoximine.