Preparation of new chiral borane-protected P,N-ferrocenyl ligands via a methoxy directedortho-lithiation

Computational study of diastereoselective ortho-lithiations of chiral ferrocenes

“…[15][16][17] Other nitrogen based ortho-directing groups are hydrazones, 18,19 azepines, 20 sulfoximines, 21 and imidazolines. 22 Oxygen performs the ortho-directing function in sulfoxides 23 acetals, 24 methoxy-derivatives, 25 and alcohols. 26 The structures of the major products of diastereoselective ortho-lithiations have been well established experimentally, either by X-ray or NMR; however, a detailed understanding of the reasons for the observed diastereoselectivity is lacking.…”

Selective Syntheses of Planar-Chiral Ferrocenes

“…The asymmetric induction was estimated to be only about 10% of that of the corresponding amine . In contrast, the group of Knochel has shown that methoxy-directed ortho lithiation at α-methoxybenzylferrocenes, such as ( R )- 101 , results almost exclusively in the formation of ( R , S p )- 102 (Scheme ). , The same holds true for the corresponding alcohols, as demonstrated by Ueberbacher et al The introduction of a methylene spacer between ferrocene and CHMeNMe 2 in ( R )- 77 decreases the diastereoselectivity of the ortho-directed lithiation. Kumada and co-workers observed with this substrate the formation of two diastereomeric 1,2-substituted ferrocenes in a 1:1 ratio …”

“…Dilithiation occurs to a lesser extent (8% yield), providing exclusively (S,S,S,S,S p ,R p )-121, which gives upon acetal cleavage an achiral meso-aldehyde (Scheme 31). 224 More than one decade after the introduction of chiral acetal (S,S)-112 into asymmetric ferrocene chemistry, Zhang and Ikeda presented 2-ferrocenyl-(S,S)-bis(methoxymethyl)-1,3-dioxolane (122), an enantiopure acetal derived from L-tartaric acid. 225 Surprisingly, treatment with n-, sec-, or t-BuLi did not result in an ortho lithiation but yielded varying amounts of carbinol 123 (up to 54% ee) and the β-elimination product 124 (Scheme 32).…”

Diastereoselective ortho-lithiation of [5]ferrocenophanes

“…Methoxy group as an ortho-directing group is also known [23]. We studied diastereoselectivity of the lithiation on (R)-1,1 0 -(1-methoxypentanediyl)ferrocene (11).…”