Catalytic Asymmetric Dihydroxylation of 1-Substituted-1-ferrocenylethenes:  An Enantioselective Entry to Chiral Tertiary Ferrocenylcarbinols and Ferrocenylalkylamines

Moreno, Rosa M.; Bueno, and Agustí; Moyano, Albert

doi:10.1021/jo052492+

Cited by 15 publications

(16 citation statements)

References 19 publications

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“…The bis(azidomethyl) compound 3 was also reduced to the bis(aminomethyl)derivative 6 with LiAlH 4 at room temperature in 98% yield (Scheme 3) by a procedure similar to reported methods [27,28].…”

Section: Resultsmentioning

confidence: 99%

Synthesis and characterization of difunctionalized derivatives of the cyclobutadiene linked dimeric cobalt sandwich compound [(η5-Cp)Co(η4-C4Ph3)]2

Mandapati

Singh

Kumar

et al. 2012

Journal of Organometallic Chemistry

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Section: Resultsmentioning

confidence: 99%

Synthesis and characterization of difunctionalized derivatives of the cyclobutadiene linked dimeric cobalt sandwich compound [(η5-Cp)Co(η4-C4Ph3)]2

Mandapati

Singh

Kumar

et al. 2012

Journal of Organometallic Chemistry

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“…[19] The most likely cause for the diminished yields of recovered olefins is therefore the oxidative degradation of the less reactive enantiomer in the reaction medium, a phenomenon that we had previously observed during the AD of slow-reacting vinylferrocenes. [8] The reaction shown in Scheme 2 also showcases another potential use of the present findings, i.e., the totally stereocontrolled preparation of ferrocene derivatives exhibiting both central and planar stereogenicity elements by AD of scalemic planar chiral vinylferro-cenes with the "matched" ligands. In order to test the generality of this concept, we submitted (+)-(R p )-1-vinyl-2-methylferrocene 1e (97:3 er, easily prepared from ferrocenecarbaldehyde by means of Kagans chiral acetal procedure; [6] note the change in the priority of the substituents with respect to vinylferrocenes 1a-d) to the same reaction conditions of Scheme 2.…”

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confidence: 57%

“…This fact can be correlated with our previous results on the AD of 1-ferrocenylethenes, that indicate a generally higher enantioselectivity for dihydroquinidine ligands. [8] Also, for the (DHQD) 2 PYR ligand, the enantioselectivity factor of the resolution decreases along the following sequence: 1a > 1c > 1b > 1d. For the (DHQ) 2 PYR ligand, the differences in enantioselectivity are less pronounced, and decrease along the sequence 1b > 1a > 1d > 1c.…”

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confidence: 96%

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Asymmetric Dihydroxylation of 2‐Substituted 1‐Vinylferrocenes: The First Non‐Enzymatic Kinetic Resolution of Planar‐Chiral Ferrocenes

et al. 2006

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The first non-enzymatic kinetic resolution of planar chiral ferrocenes has been achieved by the Sharpless catalytic asymmetric dihydroxylation (AD) of a set of racemic 2-substituted 1-ethenylferrocenes 1a-d. The enantioselectivity factor k rel varies from 20 to 62 [for (DHQD) 2 PYR ligands], and from 5 to 27 [for (DHQ) 2 PYR ligands]. The stereochemical outcome of the resolution can be easily predicted by the mnemonic device for AD, with the additional hypothesis that in the preferred transition state the olefin group and the upper cyclopentadiene ring of vinylferrocenes exhibit an essentially coplanar geometry.Keywords: asymmetric catalysis; dihydroxylation; ferrocene ligands; kinetic resolution; metallocenes More than fifty years after its discovery, ferrocene and its derivatives are still the object of unabated interest in several areas of science.[1] In particular, much effort has been devoted to the enantioselective preparation of planar-chiral 1,2-disubstituted ferrocenes, which have played a key role in the development of efficient ligands for asymmetric catalysis.[2] Up to date, the vast majority of synthetic approaches towards these compounds rely on the directed metallation of suitablely functionalized ferrocene precursors. The metallation of enantiopure ferrocenes bearing chiral, ortho-directing auxiliary groups such as alkylamines, [3] oxazolines, [4] sulfoxides, [5] or acetals [6] is the most widely used strategy, together with Snieckus enantioselective ortho-metallation of achiral ferrocenecarboxamides [7] by the butyllithium-sparteine system.Recent research from our laboratory has been focused on the synthesis of b-ferrocenyl-b-amino alcohols, a new class of central chiral ferrocene derivatives, and on the study of their synthetic applications.[8] In the course of these studies, we have made extensive use of the Sharpless asymmetric dihydroxylation [9] (AD) of 1-ferrocenylethenes. [10] We have found that in most instances this reaction takes place with good to excellent enantioselectivity, and that the ferrocenyl moiety has a strong affinity for the SW binding pocket of PYR-based ligands. In spite of the considerable controversy about the detailed mechanism of the AD process, [9] there is a general agreement on the importance of p-stacking interactions in the stabilization of the transition state (TS) complex for aryl-substituted alkenes. Theoretical calculations on the AD of styrene and of stilbene show that in the TS the phenyl and the alkene moieties present a coplanar geometry.[11] We reasoned that a similar coplanarity requirement should be operative in the AD of vinylferrocenes. If this is the case, the presence of a bulky substituent adjacent to the vinyl group would strongly destabilize one of the two limiting planar conformations of the molecule, so that for a given enantiomer of a 2-substituted 1-vinylferrocene one face of the olefin would be much more reactive than the other (see Figure 1).Thus, for the (R p )-enantiomer of a 2-substituted 1-vinylferrocene, dihydroxylation woul...

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“…12c In a similar way, several 2-amino-2-ferrocenyl alcohols 10b,c,e,g ( Figure 2) of type II were prepared from the corresponding diols in good overall yields and without loss of enantiomeric purity. 23,24,26,27 The case of amino alcohol 10g ( Figure 2) deserves some comment. The diacetylation of the corresponding diol (S)-8g proved to be very troublesome, and we decided to explore the possibility of direct azide substitution of the tertiary hydroxy group.…”

Section: Methodsmentioning

confidence: 99%

En Route to New Chiral Ferrocene Derivatives: Dead Ends, Detours, and Avenues

Moyano¹,

Rios²

2009

Synlett

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The enantioselective synthesis of b-amino-b-ferrocenyl alcohols, a new class of chiral ferrocene derivatives suitable for the elaboration of auxiliaries and ligands for asymmetric synthesis, can be efficiently achieved by the catalytic asymmetric dihydroxylation of 1-ferrocenylalkenes, followed by the regio-and stereoselective substitution of the hydroxy group adjacent to the ferrocene moiety by nitrogen nucleophiles. En route to these compounds, several previously unknown metallocene derivatives such as a-ferrocenyl epoxides, interannularly cyclopalladated ferrocenyloxazolines, and aamino-a-ferrocenyl acids have been obtained. The first examples of an organocatalytic approach to the enantioselective synthesis of chiral ferrocenes are also presented. 6

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Catalytic Asymmetric Dihydroxylation of 1-Substituted-1-ferrocenylethenes: An Enantioselective Entry to Chiral Tertiary Ferrocenylcarbinols and Ferrocenylalkylamines

Cited by 15 publications

References 19 publications

Synthesis and characterization of difunctionalized derivatives of the cyclobutadiene linked dimeric cobalt sandwich compound [(η5-Cp)Co(η4-C4Ph3)]2

Synthesis and characterization of difunctionalized derivatives of the cyclobutadiene linked dimeric cobalt sandwich compound [(η5-Cp)Co(η4-C4Ph3)]2

Asymmetric Dihydroxylation of 2‐Substituted 1‐Vinylferrocenes: The First Non‐Enzymatic Kinetic Resolution of Planar‐Chiral Ferrocenes

En Route to New Chiral Ferrocene Derivatives: Dead Ends, Detours, and Avenues

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