Sterisch gezielte Synthesen von planaren Chiroiden

Marquarding, Dieter; Klusacek, Hans; Gokel, B S George; Hoffmann, P.; Ugi, Ivar

doi:10.1002/ange.19700820910

Cited by 16 publications

(5 citation statements)

References 14 publications

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“…The most useful strategy to obtain these types of compounds in their enantiopure forms is the use of diastereoselective ortho lithiation and subsequent reaction with an appropriate coupling reagent. This asymmetric synthesis was first developed in the ferrocene series by Ugi et al by using a suitable stereogenic ortho-directing group . Kagan et al have extensively studied this strategy and found that the chiral methoxymethyl-1,3-dioxane group is very efficient for the ortho functionalization of formylferrocene …”

Section: Introductionmentioning

confidence: 99%

Synthesis of Optically Pure o-Formylcyclopentadienyl Metal Complexes of 17α-Ethynylestradiol. Recognition of the Planar Chirality by the Estrogen Receptor

et al. 2006

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A formyl group has been introduced onto the cyclopentadienyl ring of 17R-ethynylestradiol derivatives bearing a ferrocenyl, a cymantrenyl, or a cyrhetrenyl group at the ortho position with respect to the ethynyl group. The presence of this group on the cyclopentadienyl ring induces a planar chirality that provokes the formation of two diastereomers, the Sp and Rp derivatives. These compounds were prepared from Sp and Rp 1-formyl-2-iodoferrocenes, -cymantrenes, and -cyrhetrenes, which were separately prepared by using a combination of suitable ortho directing substituents, such as methoxymethyldioxane and p-tolylsulfoxide, as well as trimethylsilyl as a temporary blocking group. A cross-coupling reaction between these precursors and 17R-ethynylestradiol led to the formation of the hormone complexes. The ferrocenyl hormone compounds were only obtained from a Sonogashira reaction, the cyrhetrenyl compounds were only formed by using a Stille reaction, and the cymantrenyl compounds were obtained from both reactions. A tentative explanation for this interesting behavior is proposed. The affinity of the R diastereomers for the R receptor of estradiol is almost twice that of the S diastereomers. This is the first example of estradiol receptor discrimination between organometallic diastereomers possessing planar chirality. However, in contrast to 1,2-disubstituted derivatives, when the formyl group is at the 1,3-position, the receptor does not differentiate between the two planar chiral diastereomers.

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Section: Introductionmentioning

confidence: 99%

Synthesis of Optically Pure o-Formylcyclopentadienyl Metal Complexes of 17α-Ethynylestradiol. Recognition of the Planar Chirality by the Estrogen Receptor

et al. 2006

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“…A variety of diferrocenyl diselenides could be derived from the previously reported [ R , S ; R , S ]-bis[2-[1-(dimethylamino)ethyl]ferrocenyl] diselenide ( 2 ) [ 1 for ( R,S )-(Fc*S) 2 and 3 for ( R,S )-(Fc*Te) 2 ] 9 by several transformations. Treatment of 2 with methyl iodide afforded its ammonium salt 4 which was transformed to compound 5 in 35% overall isolated yield with complete retention of configuration by the reaction with pyrrolidine (Scheme ). , Treatment of 2 with an excess of acetic anhydride at room temperature afforded the optically pure acetate 6 of the same configuration 4 in 62% isolated yield which was then hydrolyzed to the alcohol 7 by treatment with silica gel in 60% isolated yield. Interestingly, a slow recrystallization of 7 from dichloromethane at room temperature afforded a single crystal of the diselenide having a nine-membered ring 8 and its structure was fully characterized by X-ray crystallography (Figure ) .…”

Section: Resultsmentioning

confidence: 99%

Novel Chiral Ligands, Diferrocenyl Dichalcogenides and Their Derivatives, for Rhodium- and Iridium-Catalyzed Asymmetric Hydrosilylation

et al. 1996

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As chiral ligands for transition metal complex-catalyzed asymmetric reactions, a variety of novel chiral ferrocenyl chalcogen compounds, which possess planar chirality due to the 1,2-unsymmetrically disubstituted ferrocene structure, have been prepared from chiral ferrocenes. There are seven diferrocenyl dichalcogenides (4-10), nine alkyl or aryl ferrocenyl chalcogenides (11)(12)(13)(14)(15)(16)(17)(18)(19), two bis(ferrocenylseleno)alkanes (20 and 21), two 1-(phenylchalcogeno)-1-[2-(diphenylphosphino)ferrocenyl]ethanes (22 and 24), and two 1-(phenylchalcogeno)-1-[1′,2-bis(diphenylphosphino)ferrocenyl]ethanes (23 and 25). 2,3-O,O′-Isopropylidene-2,3-dihydroxy-1,4-bis(phenylchalcogeno)butanes (26-28) are also synthesized. The Rh(I) complex-catalyzed hydrosilylation of ketones with diphenylsilane in the presence of these chiral ligands including the reported [R,S;R,S]-bis[2-[1-(dimethylamino)ethyl]ferrocenyl] dichalcogenides (1-3), followed by hydrolysis with dilute HCl, affords the corresponding chiral alcohols (R-configuration) in moderate to quantitative yield with up to 88% enantiomeric excess (ee). Similar treatment of acetophenone in the presence of diferrocenyl dichalcogenides (1, 2, 3, and 10) and a catalytic amount of Ir(I) complex gives chiral 1-phenylethanol of the opposite configuration (S) compared with the Rh case in high yield with up to 23% ee. The new complex prepared from a cationic rhodium compound and the diferrocenyl diselenide (2) shows an activity for asymmetric hydrosilylation of acetophenone to afford 1-phenylethanol in 60% chemical yield with 60% ee. Asymmetric hydrosilylation of imines and asymmetric hydrogenation of an enamide also proceed smoothly using the Rh(I)-diselenide (2) catalytic system to give the corresponding sec-amines and amide with up to 53% and 69% ee, respectively. A catalytic cycle involving the formation of tetracoordinated rhodium(I)-dichalcogenide complex (two Se and two N atoms to one Rh) followed by oxidative addition of the Si-H bond to Rh(I) and carbonyl addition to the produced rhodium(III) hydride complex is proposed for hydrosilylation of ketones.

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“…68 At the same time Ugi and co-workers introduced (R)-and (S)-N,N-dimethyl-1-ferrocenylethylamine (77, commonly known as Ugi's amine) as the starting material for diastereoselective orthodirected metalations, which proved to be a significant breakthrough in ferrocene chemistry (Scheme 22). 69,70 Resolution of (±)-77 with (R)-(+)-tartaric acid furnishes both enantiomers in 80−90% yield. Ferrocene 77 is readily deprotonated by n-BuLi in diethyl ether at 27 °C, forming after treatment with an electrophile (R,S p )-78 or (S,R p )-78 in 92% de (Scheme 22).…”

Section: ■ Electrophilic Aromatic Substitutionmentioning

confidence: 99%

“…Scheme 22. Diastereoselective Ortho-Directed Lithiation of (R)-N,N-Dimethyl-1-ferrocenylethylamine (77)69,70 …”

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confidence: 99%

Selective Syntheses of Planar-Chiral Ferrocenes

2013

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Planar-chiral ferrocenes are widely applied in catalytic asymmetric transformations in scientific research as well as in industry. A plethora of different methodologies have been developed to access these molecules with a high degree of regio- and stereoselectivity. The aim of this contribution is to give a comprehensive overview of this topic. The synthesis of 1,2- and 1,3-substituted ferrocenes by electrophilic aromatic substitution, ortho-directed metalation, kinetic resolution, and desymmetrization is discussed. Advantages and disadvantages are highlighted.

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Sterisch gezielte Synthesen von planaren Chiroiden

Cited by 16 publications

References 14 publications

Synthesis of Optically Pure o-Formylcyclopentadienyl Metal Complexes of 17α-Ethynylestradiol. Recognition of the Planar Chirality by the Estrogen Receptor

Synthesis of Optically Pure o-Formylcyclopentadienyl Metal Complexes of 17α-Ethynylestradiol. Recognition of the Planar Chirality by the Estrogen Receptor

Novel Chiral Ligands, Diferrocenyl Dichalcogenides and Their Derivatives, for Rhodium- and Iridium-Catalyzed Asymmetric Hydrosilylation

Selective Syntheses of Planar-Chiral Ferrocenes

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