Mild and reliable cleavage sequence for phenoxy acetates

Mirk, Daniela; Waldvogel, Siegfried R.

doi:10.1016/j.tetlet.2004.08.147

Cited by 21 publications

(10 citation statements)

References 17 publications

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“…Liberation of the VAPOL ligand via Curtius rearrangement [16] Hydrolysis of the EDA adduct to acid 22: A 100 mL round-bottom flask was flame dried and cooled under argon and then the VAPOL-EDA adduct 21 (232 mg, 0.372 mmol) was introduced into the flask. The adduct was dissolved in ethanol (20 mL) and then 20 % (w/v) aqueous solution of NaOH (20 mL) was added.…”

Section: Samarium Diiodidementioning

confidence: 99%

“…The filtrate was extracted once with ethyl acetate (30 mL) and the organic layers combined, washed with brine (2 30 mL), dried over MgSO 4 and then the solvent was removed via rotary evaporation to afford crude carboxylic acid product 22 as a yellow solid (217.2 mg, 0.36 mmol, 98 %). Curtius rearrangement [16] of acid 22: A 25 mL round-bottom flask was flame dried and cooled under argon and then charged with crude carboxylic acid 22 (41.2 mg, 0.069 mmol). The solid was then dissolved by the addition of toluene (3 mL) and DMF (1 mL).…”

Section: Samarium Diiodidementioning

confidence: 99%

“…The same reaction with 1.2 equivalents of EDA gives only the EDA adduct 21 in 98 % yield. The EDA adduct 21 can be recycled to optically pure (S)-VAPOL via a Curtius rearrangement [16] or by samarium diiodide reduction (Scheme 5).…”

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confidence: 99%

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Catalytic Asymmetric Aziridination with Borate Catalysts Derived from VANOL and VAPOL Ligands: Scope and Mechanistic Studies

Desai

et al. 2008

Chemistry A European J

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An extended study of the scope and mechanism of the catalytic asymmetric aziridination of imines with ethyl diazoacetate mediated by catalysts prepared from the VANOL and VAPOL ligands and triphenylborate is described. Nonlinear studies with scalemic VANOL and VAPOL reveal an essentially linear relationship between the optical purity of the ligand and the product suggesting that the catalyst incorporates a single molecule of the ligand. Two species are present in the catalyst prepared from B(OPh)(3) and either VANOL or VAPOL as revealed by (1)H NMR studies. Mass spectral analysis of the catalyst mixture suggests that one of the species involves one ligand molecule and one boron atom (B1) and the other involves one ligand and two boron atoms (B2). The latter can be formulated as either a linear or cyclic pyroborate and the (11)B NMR spectrum is most consistent with the linear pyroborate structure. Several new protocols for catalyst preparation are developed which allow for the generation of mixtures of the B1 and B2 catalysts in ratios that range from 10:1 to 1:20. Studies with catalysts enriched in the B1 and B2 species reveal that the B2 catalyst is the active catalyst in the VAPOL catalyzed asymmetric aziridination reaction giving significantly higher asymmetric inductions and rates than the B1 catalyst. The difference is not as pronounced in the VANOL series. A series of 12 different imines were surveyed with the optimal catalyst preparation procedure with the finding that the asymmetric inductions are in the low to mid 90s for aromatic imines and in the mid 80s to low 90s for aliphatic imines for both VANOL and VAPOL catalysts. Nonetheless, the crystallinity of the N-benzhydryl aziridines is such that nearly all of the 12 aziridine products screened can be brought to >99 % ee with a single recrystallization.

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Section: Samarium Diiodidementioning

confidence: 99%

Section: Samarium Diiodidementioning

confidence: 99%

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Catalytic Asymmetric Aziridination with Borate Catalysts Derived from VANOL and VAPOL Ligands: Scope and Mechanistic Studies

Desai

et al. 2008

Chemistry A European J

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“…[31,32] Furthermore, this substructure allows the preferential coordination of the Lewis acidic MoCl 5 reagent and modulation of the reaction pathway. [33] The dehydrodimerization reaction of 2 f leads to an isomeric mixture of 4 f and 4 f' in a total yield of 50 %. Wherein product 4 f' represents the minor component (entry 6).…”

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confidence: 99%

Oxidative Coupling of Diaryldisulfides by MoCl₅ to Thianthrenes

Spurg

Schnakenburg

Waldvogel

2009

Chemistry A European J

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“…This particular group can be efficiently removed under mild conditions 31. 32 Furthermore, this substructure allows the preferential coordination of the Lewis acidic MoCl 5 reagent and modulation of the reaction pathway 33. The dehydrodimerization reaction of 2 f leads to an isomeric mixture of 4 f and 4 f′ in a total yield of 50 %.…”

Section: Methodsmentioning

confidence: 99%

Volume strain changes of plasticized poly(vinylidene fluoride) during tensile and creep tests

Cangémi

Elkoun

G’Sell

et al. 2003

J of Applied Polymer Sci

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ABSTRACT:The volume strain changes of plasticized poly(vinylidene fluoride) during tensile and creep tests were characterized. A negative volume strain was observed. This phenomenon was ascribed to compaction taking place during mechanical testing, which further delayed the onset of plastic instability and, therefore, the cavitation process. It was suggested that this compaction was caused by the orientation of amorphous chain segments leading to material densification.

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Mild and reliable cleavage sequence for phenoxy acetates

Cited by 21 publications

References 17 publications

Catalytic Asymmetric Aziridination with Borate Catalysts Derived from VANOL and VAPOL Ligands: Scope and Mechanistic Studies

Catalytic Asymmetric Aziridination with Borate Catalysts Derived from VANOL and VAPOL Ligands: Scope and Mechanistic Studies

Oxidative Coupling of Diaryldisulfides by MoCl₅ to Thianthrenes

Volume strain changes of plasticized poly(vinylidene fluoride) during tensile and creep tests

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Mild and reliable cleavage sequence for phenoxy acetates

Cited by 21 publications

References 17 publications

Catalytic Asymmetric Aziridination with Borate Catalysts Derived from VANOL and VAPOL Ligands: Scope and Mechanistic Studies

Catalytic Asymmetric Aziridination with Borate Catalysts Derived from VANOL and VAPOL Ligands: Scope and Mechanistic Studies

Oxidative Coupling of Diaryldisulfides by MoCl5 to Thianthrenes

Volume strain changes of plasticized poly(vinylidene fluoride) during tensile and creep tests

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Oxidative Coupling of Diaryldisulfides by MoCl₅ to Thianthrenes