Synthesis, properties, and reactions with C-nucleophiles of (phenyloxazoline)-, (phenylmethanimine)-, and (benzaldehyde hydrazone)tricarbonylchromium(0) complexes

Kündig, E. Peter; Ripa, Alberto; Liu, Rongming; Amurrio, D.; Bérnardinelli, Gerald

doi:10.1021/om00033a050

Cited by 25 publications

(21 citation statements)

References 4 publications

(6 reference statements)

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“…1 H, 13 C and 31 P NMR spectra were recorded on a Bruker 400 or 500-MHz, and Varian-XL 200 spectrometers. High-resolution mass spectra (HR-MS) were measured …”

Section: Analytical Instrumentationmentioning

confidence: 99%

“…n-BuLi (FLUKA) was titrated before use according to the method of Chong [10]. Mes*PH 2 [11,12] and tricarbonyl [1,2,3,4,5,6-g-benzaldehyde]chromium [13,14] were synthesized following methods described in the literature. The synthesis of the 13 C-enriched compound was performed using 13 C-labelled benzaldehyde supplied by Cambridge Isotope Labs.…”

Section: Synthesesmentioning

confidence: 99%

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Chromium tricarbonyl complex of phosphaalkene: Crystal structure and electrochemistry of the Cr(CO)3 complex of PhC(H)PMes*, EPR and DFT studies of its radical anion

Gouverd

Brynda

Berclaz

et al. 2006

Journal of Organometallic Chemistry

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We report the synthesis, crystal structure and electrochemical behaviour of a complex in which the Ph group of the phosphaalkene PhC(H)@PMes* (Mes*: 2,4,6-tri-tert-butylphenyl) is coordinated to a chromium tricarbonyl group. The EPR spectra resulting from electrochemical and chemical reductions are described and the experimental g and hyperfine tensors ( 31 P)T, as determined from the EPR data, are compared with those predicted by DFT calculations for the radical anion (Cr(CO) 3 , PhC(H)@PMes) ÅÀ . The structural changes caused by the addition of an electron to the neutral complex are described, together with an estimation of the contribution of Cr(CO) 3 to the stabilization of the radical anion.

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“…1 H, 13 C and 31 P NMR spectra were recorded on a Bruker 400 or 500-MHz, and Varian-XL 200 spectrometers. High-resolution mass spectra (HR-MS) were measured …”

Section: Analytical Instrumentationmentioning

confidence: 99%

Section: Synthesesmentioning

confidence: 99%

Chromium tricarbonyl complex of phosphaalkene: Crystal structure and electrochemistry of the Cr(CO)3 complex of PhC(H)PMes*, EPR and DFT studies of its radical anion

Gouverd

Brynda

Berclaz

et al. 2006

Journal of Organometallic Chemistry

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“…d-Valinol was prepared by a literature method [31]. [12] were prepared as previously reported. All other chemicals were purchased from Aldrich or Fluka and were purified following standard literature procedures.…”

Section: Experimental Partmentioning

confidence: 99%

“…± As our synthetic plan required the addition of a nucleophilic acetaldehyde unit or its equivalent to the benzaldehyde complex 3, we first sought to investigate methods to achieve this transformation. We selected the benzaldimine complex 10 [12], which had been used successfully as substrate in previous dearomatization studies [1], and which had shown excellent ortho-selectivity in both nucleophilic addition reactions [12] and in lithiation reactions [13]. For the nucleophilic addition, [(1Z)-2-ethoxyethenyl]lithium was chosen as the nucleophilic acetaldehyde equivalent [14].…”

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confidence: 99%

Chromium‐Mediated Dearomatization: Application to the Synthesis of Racemic 15‐Acetoxytubipofuran and Asymmetric Synthesis of Both Enantiomers

Kündig

Laxmisha

Cannas

et al. 2005

Helvetica Chimica Acta

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An efficient dearomatization process of [Cr(arene)(CO) 3 ] complexes initiated by a nucleophilic acetaldehyde equivalent is detailed. It generates in a one-pot reaction three CÀC bonds and two stereogenic centers. This process allowed a rapid assembly of a cis-decalin ring system incorporating a homoannular diene unit in just two steps starting from aromatic precursors (Scheme 2). The method was applied to the total synthesis of the eudesmane-type marine furanosesquiterpene (AE)-15-acetoxytubipofuran (2). Two routes were successfully used to synthesize the g-lactone precursor of the furan ring. The key step in the first approach was a Pd-catalyzed allylic substitution (Scheme 3), while in the second approach, an Eschenmoser ± Claisen rearrangement was highly successful (Scheme 4). The Pd-catalyzed allylic substitution could be directed to give either the (normal) product with overall retention as major diastereoisomer or the unusual product with inversion of configuration (see Table). For the synthesis of the (À)-enantiomer (R,R)-2 of 15-acetoxytubipofuran, an enantioselective dearomatization in the presence of a chiral diether ligand was implemented (Scheme 7), while the ()-enantiomer (S,S)-2 was obtained via a diastereoselective dearomatization of an arene-bound chiral imine auxiliary (Scheme 8). Chiroptical data suggest that a revision of the previously assigned absolute configuration of the natural product is required.Introduction. ± Tricarbonylchromium-mediated dearomatization provides an efficient access to polysubstituted cyclohexadienes [1]. Up to three C-substituents can be added across an arene double bond in a one-pot procedure in a regio-and stereoselective manner by a sequential nucleophilic/electrophilic addition or by a nucleophilic addition followed by an acylation/alkylation sequence [2]. This dearomatization method has seen considerable development, with recent efforts mainly directed towards asymmetric variants of this reaction to give enantiomerically enriched products. Four different asymmetric methods have been developed: asymmetric induction with complexes of arenes bearing a chiral auxiliary as substituent [3], use of arene complexes possessing planar chirality [4], use of prochiral complexes with chiral nucleophiles [5], and use of complexes containing a chiral ligand at the chromium atom [6]. Benchmark enantio-and diastereoselectivities have been obtained in dearomatizations with these methods. In all but the last method, asymmetric induction takes place during the nucleophilic addition step. The third method offers an enantioselective variant in that chirality can be centered on an external ligand rather than on the nucleophile itself, and first results of the use of substoichiometric quantities of chiral information have been realized [7].In all of the dearomatization processes mentioned above, the products possess a homoannular cyclohexadiene moiety. This subunit embedded in a cis-decalin ring

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“…We have previously shown that benzaldimine complex 16 reacts with alkyllithium reagents by 1,4-addition to give, after oxidation, ortho-substituted benzaldehydes [17]. Cr(CO) 3 Complexation can be conserved if the intermediate anionic cyclohexadienyl complex is treated with a trityl salt to effect an endo-hydride abstraction.…”

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confidence: 99%

Asymmetric Synthesis of Planar Chiral (Arene)tricarbonylchromium Complexes via Enantioselective Deprotonation by Conformationally Constrained Chiral Lithium-Amide Bases

Pache

Botuha

Franz

et al. 2000

HCA

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Dedicated to Professor Albert Eschenmoser on the occasion of his 75th birthday Enantioselective lithiation/electrophile addition reactions with eight chiral Li-amide bases, 1 ± 8, and five [Cr(arene)(CO) 3 ] complexes, 9 ± 13, were investigated. Restriction of conformational freedom in the chiral Liamide base Li-1, in general, did not result in an increase in asymmetric induction. A new route to enantiomerically enriched (75 ± 92%) planar chiral ortho-substituted benzaldehyde complexes via enantioselective lithiation of benzaldimine complexes 16 and 17 is reported. Within the (1S)-enantiomer series of osubstituted benzaldehyde complexes 18a ± d, the sign of the specific rotation, [a] 20 D , is found to be positive, except for the trimethylstannyl derivative 18b. This is interpreted in terms of a reversed conformation of the aldehyde group.

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Synthesis, properties, and reactions with C-nucleophiles of (phenyloxazoline)-, (phenylmethanimine)-, and (benzaldehyde hydrazone)tricarbonylchromium(0) complexes

Cited by 25 publications

References 4 publications

Chromium tricarbonyl complex of phosphaalkene: Crystal structure and electrochemistry of the Cr(CO)3 complex of PhC(H)PMes*, EPR and DFT studies of its radical anion

Chromium tricarbonyl complex of phosphaalkene: Crystal structure and electrochemistry of the Cr(CO)3 complex of PhC(H)PMes*, EPR and DFT studies of its radical anion

Chromium‐Mediated Dearomatization: Application to the Synthesis of Racemic 15‐Acetoxytubipofuran and Asymmetric Synthesis of Both Enantiomers

Asymmetric Synthesis of Planar Chiral (Arene)tricarbonylchromium Complexes via Enantioselective Deprotonation by Conformationally Constrained Chiral Lithium-Amide Bases

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