New efficient synthesis of Taniaphos ligands: application in ruthenium- and rhodium-catalyzed enantioselective hydrogenations

Tappe, Katja; Knöchel, Paul

doi:10.1016/j.tetasy.2003.11.004

Cited by 80 publications

(49 citation statements)

References 33 publications

(11 reference statements)

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“…Under these conditions, we were able to obtain the pure ( S )‐ 7 , 10 and 15 (using ( R )‐Me‐CBS), and ( R )‐ 11 , 14 and 18 (using ( S )‐Me‐CBS) in good yields (to simplify the description we omit the configuration of the biotin heterocycle moiety, which is fixed as (3a S ,4 S ,6a R ) and the desthiobiotin moiety which is fixed as (4 R ,5 S )). As expected, the stereochemistry of the carbon atom α to the ferrocenyl moiety of the obtained alcohols was the same as that obtained in the reduction of acetylferrocene using CBS‐oxazaborolidine with borane as a reducing agent . The stereochemistry of alcohols 11 and 14 was also confirmed by X‐ray crystallography, and the sole formation of diastereoisomers was confirmed by 1 H NMR spectroscopy.…”

Section: Resultssupporting

confidence: 76%

“…Consequently, we decided to use a chiral reducing agent. We chose the Corey–Bakshi–Shibata (CBS) reduction methodology using ( R )‐Me‐CBS‐oxazaborolidine [( R )‐Me‐CBS] and ( S )‐Me‐CBS‐oxazaborolidine [( S )‐Me‐CBS] with borane–THF complex at 0 °C as the reducing agents . If typical catalytic amounts (1–30 mol %) of ( S )‐ or ( R )‐Me‐CBS were used, only trace amounts of the desired products were formed.…”

Section: Resultsmentioning

confidence: 99%

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Ferrocene–Biotin Conjugates: Synthesis, Structure, Cytotoxic Activity and Interaction with Avidin

et al. 2016

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Friedel–Crafts acylation of ferrocene with d‐biotin, d‐homobiotin and d‐desthiobiotin gave ferrocenyl ketones. These compounds were diastereoselectively reduced to the corresponding alcohols using (R)‐ and (S)‐Me‐CBS‐oxazaborolidine–borane complexes as reducing agents. The alcohols were further transformed into azido and finally to amino derivatives with retention of configuration, as confirmed by X‐ray crystallography. Ferrocenylbiotin alcohols smoothly underwent dehydration to (E)‐alkenes as the major isomers by heating in diluted acetic acid. The synthesized compounds retained high affinity for avidin. They also exhibited high cytotoxicity toward cancer cells expressing various levels of sodium‐dependent multivitamin transporter (SMVT) in the absence of biotin in the medium, whereas the presence of free biotin decreased their antiproliferative activity. This revealed that these biotin–ferrocene conjugates might be used as biologically active agents against cancer cells, although there was no clear relationship between their cytotoxicity and cellular SMVT level.

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Section: Resultssupporting

confidence: 76%

Section: Resultsmentioning

confidence: 99%

Ferrocene–Biotin Conjugates: Synthesis, Structure, Cytotoxic Activity and Interaction with Avidin

et al. 2016

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“…After the reaction was complete all volatile compounds were removed in vacuo and the remaining solid was extracted with 2 Â 20 mL of diethylether-n-pentane mixture (3 : 1 v/v). After removing the solvent from the filtrates methyl 5-phenyl- [1,4,2]diazaphospholo [5,4- Compound 5b was prepared following the same procedure as described for 5a starting from 2-amino-3-(2-ethoxy-2-oxoethyl)-4-phenyl-1,3-thiazol-3-ium bromide (3b) (0.34 g, 1 mmol, 1.0 eq. ), trichlorophosphine (87.3 mL, 1 mmol, 1.0 eq.)…”

Section: -Phenyl-[142]diazaphospholo[54-b][13]thiazole (2a) In mentioning

confidence: 99%

New anellated 4H-1,4,2-diazaphospholes

2013

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2a with two equivalents of water yields the corresponding zwitterionic phosphinate 9, the structure of which was elucidated by single crystal X-ray diffraction. The structure in the solid state is governed by strong N-HÁ Á ÁO hydrogen bonding resulting in chains along the crystallographic a-axis. The chloroform molecules are integrated in the chains by weaker C-HÁ Á ÁO bonds and C-ClÁ Á ÁC halogen bonds.

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“…The recent introduction of the TaniaPhos ligands (34) provides another excellent catalyst system for the reduction of dehydroamino acid derivatives and enol acetates [150][151][152][153]. One surprise is that the sense of induction in the product is opposite that observed with a JosiPhos-derived catalyst [125].…”

Section: Ferrocene Ligandsmentioning

confidence: 99%

Enantioselective Alkene Hydrogenation: Introduction and Historic Overview

Ager¹

2006

The Handbook of Homogeneous Hydrogenation

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23Enantioselective Alkene Hydrogenation: Introduction and Historic Overview Development of CAMP and DIPAMPDuring the late 1960s, Horner et al. [13] and Knowles and Sabacky [14] independently found that a chiral monodentate tertiary phosphine, in the presence of a rhodium complex, could provide enantioselective induction for a hydrogenation, although the amount of induction was small [15][16][17][18][19][20]. The chiral phosphine ligand replaced the triphenylphosphine in a Wilkinson-type catalyst [10,21,22]. At about this time, it was also found that [Rh(COD) 2 ] + or [Rh(NBD) 2 ] + could be used as catalyst precursors, without the need to perform ligand exchange reactions [23].Knowles found that the monophosphine CAMP (1a) could provide an ee-value of up to 88% for the reduction of dehydroamino acids. CAMP was an extension of PAMP (1b) that provides ee-values of 50-60% in analogous reactions [24]. At this time, Kagan showed that DIOP (2) (vide infra), where the stereogenic centers are not at phosphorus, could also provide enantioselective induction in an hydrogenation. DIOP also showed that a bisphosphine need not have the chirality at phosphorus, and that good stereoselectivity might result from a C 2 -symmetric ligand. Knowles then developed the C 2 -symmetric ligand DIPAMP (3) [22,25]. The use of Rh-DIPAMP for the synthesis of l-Dopa is well known and is still practiced today [12,22,27]. A number of variations of the DIPAMP structure were investigated for the synthesis of this important pharmaceutical, but the parent remains the best ligand in this class [22].

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New efficient synthesis of Taniaphos ligands: application in ruthenium- and rhodium-catalyzed enantioselective hydrogenations

Cited by 80 publications

References 33 publications

Ferrocene–Biotin Conjugates: Synthesis, Structure, Cytotoxic Activity and Interaction with Avidin

Ferrocene–Biotin Conjugates: Synthesis, Structure, Cytotoxic Activity and Interaction with Avidin

New anellated 4H-1,4,2-diazaphospholes

Enantioselective Alkene Hydrogenation: Introduction and Historic Overview

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