Study Concerning the Effects of Chelation on the Structure and Catalytic Activity of Ruthenium Carbene Complexes

Fürstner, Alois; Thiel, Oliver R.; Lehmann, Christian W.

doi:10.1021/om0108503

Cited by 131 publications

(59 citation statements)

References 49 publications

(22 reference statements)

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Finally, one has to keep in mind that polar substituents in the substrate that are able to chelate the incipient metal carbene intermediates can strongly impact the effectiveness of RCM-based macrocyclizations. [19,20] Because these issues, collectively, discourage an RCM approach to 1, [8] we envisaged the formation of its 28-membered ring at C-14/C-15 by an a priori less ambiguous ring closing alkyne metathesis (RCAM) reaction. [21,22] However, this strategic decision also bore considerable risk.…”

Section: Resultsmentioning

confidence: 99%

“…A standard extractive work up followed by flash chromatography (hexanes/EtOAc 4:1) afforded product 15 (117 mg, 90 %) as a colorless oil. 1 A C H T U N G T R E N N U N G (17Z)-18-Methoxymethyl-oxa-cyclooctacos-17-en-15-yne-2,10-dione (16): Complex 20 (7.5 mg, 0.016 mmol) [20] , [59] and CH 2 Cl 2 (120 mL, 1.87 mmol) were successively added to a solution of diyne 15 (60 mg, 0.12 mmol) in toluene (85 mL) and the resulting mixture was stirred at 80 8C for 15 h. For work up, the reaction was quenched with MeOH (5 mL), all volatile materials were evaporated and the residue was purified by flash chromatography (hexanes/ (6).…”

Section: -Methoxymethoxy-hexadec-2-yn-8-ol (8)mentioning

confidence: 99%

See 1 more Smart Citation

Total Synthesis of Myxovirescin A₁

Fürstner¹,

Bonnekessel²,

Blank³

et al. 2007

Chemistry A European J

Self Cite

View full text Add to dashboard Cite

A convergent total synthesis of the antibiotic macrolide myxovirescin A1 (1) is described that is largely based on reagent- and catalyst-controlled transformations. This includes a highly regioselective Negishi reaction of dibromo-alkene 48 with an alkynylzinc reagent, and a palladium catalyzed alkyl-Suzuki coupling of the resulting enyne derivative 12 with the 9-BBN-adduct derived from alkene 61. The latter was obtained via an asymmetric hydrogenation of the chlorinated beta-ketoester 49 and an anti-selective oxyallylation of the functionalized aldehyde 53 as the key steps. The preparation of the bis-borylated allyl-donor 57 used in the oxyallylation step, however, required careful optimization and led to important insights into the nature of the classical hydroborating agent "di(isopinocampheyl)borane (Ipc2BH)". It was unambiguously shown by X-ray crystallography that in the solid state this compound is dimeric, but it is prone to undergo an essentially quantitative mono-deborylation when dissolved in CH2Cl2 or benzene; its composition in ethereal solvents is even more complex as evident from 11B NMR data. Product 71 derived from 12 and 61 was elaborated into the enyne-yne derivative 75, which served as the substrate for an exquisitely selective ring closing alkyne metathesis reaction (RCAM) catalyzed by the molybdenum tris-amido complex 20 activated in situ with CH2Cl2. The resulting cyclic enyne 76 was subjected to a ruthenium catalyzed trans-hydrosilylation/proto-desilylation tandem. Although [Cp*Ru(MeCN)3]PF6 had previously been recommended as catalyst of choice for trans-hydrosilylation reactions of internal alkynes, this complex failed to afford the desired product, whereas its sterically less hindered congener [CpRu(MeCN)3]PF6 permitted the reaction to be performed in appreciable yield, but at the expense of a lower stereoselectivity. AgF-mediated proto-desilylation of the isomeric silanes 79 and 80 followed by cleavage of the remaining acetal protecting groups afforded myxovirescin A1 and its hitherto unknown 14Z-isomer 81, respectively.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: -Methoxymethoxy-hexadec-2-yn-8-ol (8)mentioning

confidence: 99%

Total Synthesis of Myxovirescin A₁

Fürstner¹,

Bonnekessel²,

Blank³

et al. 2007

Chemistry A European J

Self Cite

View full text Add to dashboard Cite

show abstract

“…Chelation sequesters the catalyst in an unproductive form ( Figure 5A, a) and therefore slows the polymerization rate. 71 For methyl-substituted endo,endoand exo,exo-norbornenyl diesters (2a and 3a, respectively), the ground-state potential energy surfaces corresponding to one productive ROMP cycle were computed ( Figures 5B and S9). The relative free energies at 298 K (ΔG) indicate that formation of the six-membered chelate is more favorable for the endo isomer (ΔΔGchelate = 9.64 kcal mol −1 ) than for the exo isomer (ΔΔG-chelate = 5.87 kcal mol −1 ).…”

Section: Chart 1 Monomer Design For Ring-opening Metathesis Copolymementioning

confidence: 99%

Design, Synthesis, and Self-Assembly of Polymers with Tailored Graft Distributions

et al. 2017

View full text Add to dashboard Cite

Grafting density and graft distribution impact the chain dimensions and physical properties of polymers. However, achieving precise control over these structural parameters presents long-standing synthetic challenges. In this report, we introduce a versatile strategy to synthesize polymers with tailored architectures via grafting-through ring-opening metathesis polymerization (ROMP). One-pot copolymerization of an ω-norbornenyl macromonomer and a discrete norbornenyl co-monomer (diluent) provides opportunities to control the backbone sequence and therefore the side chain distribution. Toward sequence control, the homopolymerization kinetics of 23 diluents were studied, representing diverse variations in the stereochemistry, anchor groups, and substituents. These modifications tuned the homopolymerization rate constants over two orders of magnitude (0.36 M −1 s −1 < khomo < 82 M −1 s −1 ). Rate trends were identified and elucidated by complementary mechanistic and density functional theory (DFT) studies. Building on this foundation, complex architectures were achieved through copolymerizations of selected diluents with a poly(D,L-lactide) (PLA), polydimethylsiloxane (PDMS), or polystyrene (PS) macromonomer. The cross-propagation rate constants were obtained by non-linear least squares fitting of the instantaneous co-monomer concentrations according to the Mayo-Lewis terminal model. Indepth kinetic analyses indicate a wide range of accessible macromonomer/diluent reactivity ratios (0.08 < r1/r2 < 20), corresponding to blocky, gradient, or random backbone sequences. We further demonstrated the versatility of this copolymerization approach by synthesizing AB graft diblock polymers with tapered, uniform, and inverse-tapered molecular "shapes." Small-angle X-ray scattering analysis of the self-assembled structures illustrates effects of the graft distribution on the domain spacing and backbone conformation. Collectively, the insights provided herein into the ROMP mechanism, monomer design, and homo-and copolymerization rate trends offer a general strategy for the design and synthesis of graft polymers with arbitrary architectures. Controlled copolymerization therefore expands the parameter space for molecular and materials design.

show abstract

“…[19] Deactivation of the metal centre can occur through coordination of the ester carbonyl to the metal centre in the alkylidene intermediate. [20] The desired compounds were readily available through a threestep synthetic sequence, starting form commercially available allylglycine. [21] The RCM of the allylglycine derivatives were carried out under the standard conditions and the results have been summarized in Table 5.…”

Section: Full Papersmentioning

confidence: 99%

Unexpected Results of a Turnover Number (TON) Study Utilising Ruthenium-Based Olefin Metathesis Catalysts

Maechling

Zaja

Blechert

2005

Advanced Synthesis & Catalysis

View full text Add to dashboard Cite

A turnover number (TON) study of ruthenium-based metathesis catalysts has been conducted for ring-closing metathesis (RCM) in dilute solution.Unexpectedly the results indicate that 1 st generation metathesis catalysts can give higher TON in RCM of simple unsubstituted terminal olefins than their second generation counterparts. In particular, the 1 st generation Hoveyda-Grubbs catalyst showed unexpectedly high activity, particularly when compared to the 2 nd generation catalysts.

show abstract

Study Concerning the Effects of Chelation on the Structure and Catalytic Activity of Ruthenium Carbene Complexes

Cited by 131 publications

References 49 publications

Total Synthesis of Myxovirescin A₁

Total Synthesis of Myxovirescin A₁

Design, Synthesis, and Self-Assembly of Polymers with Tailored Graft Distributions

Unexpected Results of a Turnover Number (TON) Study Utilising Ruthenium-Based Olefin Metathesis Catalysts

Contact Info

Product

Resources

About

Study Concerning the Effects of Chelation on the Structure and Catalytic Activity of Ruthenium Carbene Complexes

Cited by 131 publications

References 49 publications

Total Synthesis of Myxovirescin A1

Total Synthesis of Myxovirescin A1

Design, Synthesis, and Self-Assembly of Polymers with Tailored Graft Distributions

Unexpected Results of a Turnover Number (TON) Study Utilising Ruthenium-Based Olefin Metathesis Catalysts

Contact Info

Product

Resources

About

Total Synthesis of Myxovirescin A₁

Total Synthesis of Myxovirescin A₁