Asymmetric Synthesis of Novel Ferrocenyl Ligands with Planar and Central Chirality

Abstract

A stereogenic center at the position beta to the metallocene backbone is present in ferrocenyl ligands 2, which are interesting for asymmetric catalysis. These planar-chiral compounds are accessible for the first time by a highly diastereoselective and enantioselective synthesis (de=93-97 %; ee>/=96 %) from the ferrocenyl ketones 1. A variety of donor groups (E(1)=Ph(2)P small middle dotBH(3), SMe, SiPr; E(2)=SMe, STol, SePh, Ph(2)P small middle dotBH(3), iPr(2)P small middle dotBH(3)) can be introduced as electrophiles. Tol=tolyl=CH(3)C(6)H(4).

Chiral Auxiliaries - Principles and Recent Applications

“…88a In addition, these hydrazine auxiliaries can be used in various organic reactions such as aldol reactions, 89 Michael additions, 90 rearrangements, 91 nucleophilic addition reactions to the C=N double bond, 92 Diels-Alder reactions 93 and synthesis of organometallic substrates like substituted ferrocenes. 94,95 Some important recent advances are presented in the following paragraphs.…”

“…Ferrocenyl ligands are of increasing interest for asymmetric catalysis in academia and industry. 95 Therefore, the asymmetric synthesis of planar-or central chiral ferrocenes with phosphorus, sulfur and nitrogen substituents is an important goal. Starting from SAMP-derived hydrazones 106, Enders et al successfully used the auxiliary to control central as well as planar chirality in the synthesis of ferrocenes 109 (Scheme 41).…”

“…Starting from SAMP-derived hydrazones 106, Enders et al successfully used the auxiliary to control central as well as planar chirality in the synthesis of ferrocenes 109 (Scheme 41). 95 Subsequent functionalization of the side chain of 107 and of the ortho-position in 108 can be executed with several electrophiles. The first deprotonation is carried out with LDA, whereas a stronger lithium base has to be used for the directed ortho-metallation.…”

Bildung und Kristallstruktur von FcCH(t-Bu)NHCH(Me)CH2OMe · LiI · Et2O

“…1 bildet monomere Moleku È le aus, bei denen auûer vander-Waals-, keine anderen intermolekularen Wechselwirkun- 3 ]I zur Bildung separater tetraedrisch bzw. oktaedrisch koordinierter Li + -und I ± -Ionen [12,13].…”

Temperature-controlled switchable preparation of ferrocene bis(oxazoline-phosphine) ligands with different planar chiralities and their coordination behaviors

“…Enders has reported an interesting chiral hydrozone-induced diastereoselective ortho-functionalization of forrencene. 12 Planar chiral ferrocene ligands possessing P,P and P,N coordinating groups have attracted much attention due to their use in organometallic catalysis. 2 Following Ugi's procedure, Hayashi/ Kumada prepared the first planar chiral ferrocene ligand PPFA (Fig.…”