Enantiopure Ferrocene‐Based Planar‐Chiral Iridacycles: Stereospecific Control of Iridium‐Centred Chirality

Arthurs, Ross A.; Ismail, Muhammad; Prior, Christopher; Oganesyan, Vasily S.; Coles, Simon J.; Richards, Christopher J.

doi:10.1002/chem.201504458

Cited by 27 publications

(53 citation statements)

References 88 publications

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“…In contrast, doubly silylated 10 was recovered unchanged from the reaction. That desilylation of 9 does not occur on iridacycle formation had been determined previously with the isolation of 11, 11 the TMS blocking group resulting in the opposite sense of planar chirality. The absence of reaction with 10 is consistent with the two blocking groups preventing iridacycle formation, and thus generation of an iridocenium cation.…”

Section: Scheme 4 Synthesis Of Iridoceniumcarbaldehydementioning

confidence: 59%

“…For the cation derived from 5 calculations give an iridium-iron bonding parameter of 1.25, and partial charge delocalisation onto iron. 11 A possible mechanism for the loss of CpFe + is via migration of this moiety onto iridium, and iron ligation by the nitrile solvent and/or hydroxide/water. 17 The resulting neutral and resonance-stabilised cyclopentadienyl-iridacycle can coordinate water to give 13 from which can occur reversible proto-deiridation.…”

Section: Scheme 4 Synthesis Of Iridoceniumcarbaldehydementioning

confidence: 99%

“…12 Replacement of benzonitrile by trimethylacetonitrile also resulted in the generation of 3 (47% The cationic iridacycle 4, containing a coordinated acetonitrile ligand, is available from 1 by a reduction in the quantity of base employed (either NaOH or KO t Bu) to one equivalent on reaction with [Cp*IrCl 2 ] 2 and KPF 6 for 18 hours (Scheme 3). 11 Reexamination of the synthesis of 4 employing NaOH as base, with an increase in the reaction time to 24 h at 45 o C, revealed a 5 : 1 ratio of 4 : 3 following work-up. 13 With a 5 day reaction time the ratio of 4 : 3 was 1 : 1.…”

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confidence: 99%

“…Secondly, and in contrast to the stability of neutral imine-based iridacycle 5, 11 the cationic complex that results from chloride abstraction with AgPF 6 transformed over a period of 1 day into iridoceniumcarbaldehyde 6 (Scheme 4 CN), the aldehyde moiety arising from facile aldimine hydrolysis under the conditions used for product isolation.…”

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confidence: 99%

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Metallocene to metallocene conversion. Synthesis of an oxazoline-substituted pentamethyliridocenium cation from a ferrocenyloxazoline

2016

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Reaction of (S)-2-ferrocenyl-4-(1-methylethylMetallocenes comprise one of the most important class of compounds in organometallic chemistry. Many catalysts and ligands are based on these complexes that contain an element, usually a transition metal, sandwiched between two η 5 -cyclopentadienyl rings.1 Homoleptic metallocenes are made typically from the reaction of a cyclopentadiene or a cyclopentadienyl complex with a suitable metal precursor, 2 and these methodologies have been adapted widely to the synthesis of heteroleptic metallocenes.3 The starting cyclopentadienyl complexes used generally contain an sblock element and are largely ionic in character, with examples including CpLi, CpNa and Cp 2 Mg. The use of the latter magnesium complex for the synthesis of ferrocene etc 4 is a very specific type of transmetallation, a metallocene to metallocene conversion where the two complexes are based on a different metal. 5 Other examples of this type of transformation appear to be rare, [6][7][8] in particular, the transformation of one air, moisture and thermally stable d-block based complex into another. 9 In this communication we describe the conversion of substituted ferrocene derivatives into substituted iridocenium cations, 10 reactions that proceed via the intermediacy of planar chiral iridacycles.We recently reported that reaction of ferrocenyloxazoline 1 with [Cp*IrCl 2 ] 2 in acetonitrile with 4 equivalents of KPF 6 and 4 equivalents of NaOH results in the formation of a single diastereoisomer of neutral iridacycle 2 containing a cyanomethyl ligand (Scheme 1). 11Scheme 1 Highly diastereoselective synthesis of planar chiral and chiral-at-metal iridacycle 2.

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Section: Scheme 4 Synthesis Of Iridoceniumcarbaldehydementioning

confidence: 59%

Section: Scheme 4 Synthesis Of Iridoceniumcarbaldehydementioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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Metallocene to metallocene conversion. Synthesis of an oxazoline-substituted pentamethyliridocenium cation from a ferrocenyloxazoline

2016

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“…16 These uses of deuterium as a removable blocking group illustrate how this methodology enables the rapid stereoselective synthesis of multiple substituted ferrocene derivatives.…”

Section: Scheme 4 Reaction Of (Sr P )-2-d-3ementioning

confidence: 99%

Deuterium as a Stereochemically Invisible Blocking Group for Chiral Ligand Synthesis

Arthurs

Richards

2017

Org. Lett.

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ABSTRACT:Highly diastereoselective lithiation (s-BuLi/TMEDA in Et 2 O, -78 o C, 2 h) of (S)-2-ferrocenyl-4-(substituted)oxazolines followed by addition of MeOH-d 4 , gave up to 95% D incorporation. Subsequent application of alternative lithiation conditions (n-BuLi in THF, -78 o C, 2 h), followed by addition of an electrophile, resulted in a reversal of diastereoselectivity controlled primarily by the high k H /k D value for lithiation (isomer ratio typically between 10:1 and 20:1).Many non-racemic ligands employed in metal catalyzed asymmetric reactions contain more than one element of chirality. For a C 1 -symmetric ligand containing two such elements, diastereoisomers are possible which may result in different reaction product enantioselectivities, and there are a number of examples where the identification of matched and mismatched chirality pairings has been established.

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Asymmetric CH Functionalization of Ferrocene

Jin¹

2022

Handbook of CH-Functionalization

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Since the milestone discovery of its sandwich‐type scaffold in the early 1950s, ferrocene and its related organometallic compounds have received enormous interest from chemistry, biology, and material communities. The rigid molecular architecture and aromaticity make them relatively stable and applicable as catalysts or ligands for the diverse organic transformations. To date, a wide range of synthetic methodologies for this unique family of organometallic compounds have been developed, given their widespread application in organic synthesis. Among them, the recent direct CH functionalization catalyzed by transition metals provided an atom‐ and step‐economical approach to the structurally diverse ferrocene derivatives. In particular, transition metal‐catalyzed asymmetric CH functionalization of ferrocene has proven an efficient, enantioselective strategy for the synthesis of planar‐chiral ferrocenes. In this article, the recent progress on direct asymmetric CH functionalization of ferrocene derivatives is summarized.

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Enantiopure Ferrocene‐Based Planar‐Chiral Iridacycles: Stereospecific Control of Iridium‐Centred Chirality

Cited by 27 publications

References 88 publications

Metallocene to metallocene conversion. Synthesis of an oxazoline-substituted pentamethyliridocenium cation from a ferrocenyloxazoline

Metallocene to metallocene conversion. Synthesis of an oxazoline-substituted pentamethyliridocenium cation from a ferrocenyloxazoline

Deuterium as a Stereochemically Invisible Blocking Group for Chiral Ligand Synthesis

Asymmetric CH Functionalization of Ferrocene

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