Diastereoselective synthesis and coordination chemistry of enantiopure keto-bis-(2-phosphametallocene)s

Carmichael, Duncan; Goff, Xavier F. Le; Müller, E.; Ricard, Louis; Stankevič, M.

doi:10.1039/c2dt11647b

Cited by 7 publications

(2 citation statements)

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“…The study here is interesting because the interception of a quite strongly bound intermediate 9 sheds some light upon the reaction trajectory for the coordination of phospholide anions to late transition metal centres and also provides a rationale for a near‐perfect diastereoselectivity that is observed during the formation of 10 . Strong literature evidence suggests that the reaction of phospholide anions with late transition metal complexes involves the transient formation of η 1 ‐coordinated phospholides,30–33 and this incipient η 1 ‐coordination might reasonably be expected to impose a degree of selectivity upon the reaction trajectory for the incoming metal centre. In situ NMR spectroscopic studies showed that careful treatment of phospholide 8 with two equivalents of [FeCp*(Cl)tmeda] under mild conditions (THF, 25 °C) led to complex intermediate 9 (Figure 2) quantitatively, but isolation proved difficult and single crystals suitable for characterisation could only be obtained in low yield.…”

Section: Resultsmentioning

confidence: 99%

“…We have been interested for some time in the homologation of phosphametallocenes, and the chemistry described here indicates that autotemplation may allow access to these compounds in relatively specific fashion. Whilst the precise roots of this templation are not clear at present, it should be noted that a similar diastereoselectivity is not observed in the absence of templating for the preparation of ketone‐bridged 2,2′‐keto‐bis(2‐phosphametallocene)s 33. Trinuclear phosphametallocenes are a previously unknown class, and the stability of 10 , both thermally and in air, bodes well for the preparation of more extended arrays; these seem likely to be accessible given that the protocol begins and ends with carboxymethyl‐substituted phosphametallocenes.…”

Section: Discussionmentioning

confidence: 97%

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Oligo(metallocene)s Containing Keto‐Bridged Phospholyl Rings

2013

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 97%

Oligo(metallocene)s Containing Keto‐Bridged Phospholyl Rings

2013

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Unsaturated Organic Derivatives of Phosphaferrocene – Synthesis and Reactivity of Vinyl‐ and Alkynylphosphaferrocenes

2012

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Starting from 2-formyl-3,4-dimethylphosphaferrocene, a series of vinyl-substituted phosphaferrocenes was prepared by Wittig and related olefination reactions. The parent 3,4dimethyl-2-vinylphosphaferrocene (2) could be selectively converted to either the terminal or branched alcohols 8b and 8a by hydroboration/oxidation or protonation in aqueous solution, respectively. Elimination of HBr from 2-bromovinylphosphaferrocene 9 provided access to the 2-ethynylphosphaferrocene derivative 10, which could be converted to other alkynes by deprotonation and electrophilic quench. Additionally, the syntheses of the 2-cyano-(15) and 2-Synthesis and Reactivity of Vinyl-and Alkynylphosphaferrocenes Scheme 1. Preparation of the vinylphosphaferrocene derivative 2.are easily accessible by Horner-Wadsworth-Emmons reactions (Scheme 2). [7] The desired phosphonates were obtained from triethyl phosphite and the respective bromo compound and were subsequently deprotonated with nBuLi or NaH prior to addition of the aldehyde. The acrylic ester 3 was obtained solely as the E isomer, whereas for the acrylonitrile 4 an E/Z ratio of 10:1 was observed. Scheme 2. Preparation of acrylic derivatives 3 and 4.The presence of the phosphorus atom affects the appearance of the 1 H NMR spectrum of the vinyl group in compound 2; the signal for the CH proton is additionally split due to a 3 J HP coupling of 10.5 Hz, whereas the trans proton of the CH 2 group experiences a 4 J HP coupling of 1.8 Hz.No H-P coupling was observed for the cis CH 2 proton. The acrylic ester 3 could be reduced to give the saturated compound 5 by treatment with NaBH 4 in the presence of CuCl [8] and was finally hydrolyzed to the propionic acid 6 (Scheme 3).Scheme 3. Preparation of propionic acid derivatives 5 and 6.Commencing from 2, the isomeric 2-(phosphaferrocenyl)ethanols 8a and 8b could be prepared. Thus, hydroboration of 2 yields the anti-Markownikow organoborane 7 as a mixture of diastereomers due to the racemic nature of compound 2. However, treatment with alkaline hydrogen peroxide cleanly afforded the linear alcohol 8b in 69 % overall yield, an alternative synthesis of which has been reported by our group before. [9] On the contrary, the branched isomer 8a was obtained by treatment of the vinyl derivative 2 with aqueous hydrochloric acid (Scheme 4). Presumably, the Eur.

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Synthesis of Monophosphaferrocenes Revisited

et al. 2022

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The method of preparing monophosphaferrocenes originally reported by Roberts and Wells, which requires two equivalents of [(mesitylene)FeCp]PF6 (A), was reinvestigated. By the use of inexpensive aluminum chloride as a phenyllithium scavenger, a 50 % reduction of required A could be attained. Diverse monophosphaferrocene derivatives having aliphatic C‐substituents, including four new compounds, were prepared in good yields from the corresponding P‐phenylphospholes, A (1 equiv.), and aluminum chloride (1/3 equiv.) under the modified conditions. These modified conditions showed comparable to better yields of monophosphaferrocenes and the far better atom‐economy compared to the original conditions.

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Diastereoselective synthesis and coordination chemistry of enantiopure keto-bis-(2-phosphametallocene)s

Cited by 7 publications

References 102 publications

Oligo(metallocene)s Containing Keto‐Bridged Phospholyl Rings

Oligo(metallocene)s Containing Keto‐Bridged Phospholyl Rings

Unsaturated Organic Derivatives of Phosphaferrocene – Synthesis and Reactivity of Vinyl‐ and Alkynylphosphaferrocenes

Synthesis of Monophosphaferrocenes Revisited

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