Stereoselective syntheses. VI. Correlation of central and planar chirality in ferrocene derivatives

Abstract

1 -Ferrocenylethyldimethylamine ( 7) is readily obtained from 1 -ferrocenylethanol by treatment with phosgene and then dimethylamine. The resolution of 7 with (i?)-(+)-tartaric acid is particularly easy and both antipodes are obtained in high yield. Qualitatively the steric course of the lithiation 7 -> 8 is predictable and proceeds with high stereoselectivity (96:4). Subsequent reactions of 8 with trimethylchlorosilane, formaldehyde, or benzophenone produce 9a-c. The quaternization of 9 in the presence of nucleophiles leads to substitution of the dimethylamino group in 9 with complete configurational retention, which is confirmed by nmr and the cycle {9a, 10, 14,13 j. The retention is due to the ease of formation of 11 and its configurational stability under suitable conditions. The reactions presented here provide a basis for convenient, predesignated stereoselective syntheses and

Synthesis of planar chiral ferrocenyl sulfides and evaluation as catalysts for the asymmetric epoxidation of aldehydes

“…32,33 Amine 3 and sulfoxide 2 have been reported 25,32 to undergo ortho-deprotonation with high diastereoselectivity in presence of a strong base. We have used this property to synthesize compounds 4 and 6 ( Figure 2).…”

“…Deprotonation of the amine 3 was effected by n-BuLi under conditions reported by Ugi and his group. 32 The metallated ferrocene was sulfanylated by dimethyl-or dicyclohexyl-disulfides to lead to aminosulfides 6a 32 and 6b. Very modest yields of pure materials, respectively 21 and 38%, were obtained as a result of the crystallization required for purification.…”

Ferrocene-derived P,N ligands: synthesis and application in enantioselective catalysis

“…This method was first demonstrated by Ugi with the lithiation of chiral [1-(N (12), also called Ugi's amine [29]. High diastereoselectivity is provided as a result of the sterical repulsion between the methyl substituent and the ferrocene moiety in the unfavored diastereomer (Scheme 4).…”

The synthesis and structure of

“…We also have an interest in exploring the electrochemistry of chiral surfaces (7,8). For these reasons the synthesis of l c , which contains both a chiral center and planar chirality, and its binding to silica, was an attractive target since, if necessary, it could readily be prepared as an optically pure enantiomer (9,10).…”