Cleavage of Ethers

Bhatt, M. V.; Kulkarni, Surendra U.

doi:10.1055/s-1983-30301

Cited by 420 publications

(192 citation statements)

References 83 publications

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“…Cyanates may adhere to a variety of substrates, e.g. metals, glass and carbon fibres and cyanate adhesives have yielded values of [14][15][16][17][18][19][20] MPa (for lap shear strength) on 20224 T-3 aluminium alloy (some 50-100% higher than corresponding BADGE and TGDDM epoxy adhesives (cured with aromatic diamines), but it is their behaviour on silicon that is of particular interest in the microelectronics arena because of the ubiquity of this material in the formation of MCMs. Typically, the latter are formed from sequentially built layers of metallised conductors on ceramic or silicon substrates and unreinforced polymer dielectric films.…”

Section: Introductionmentioning

confidence: 99%

“…For example, having produced (bis-4-(4-methoxyphenoxy) phenylethoxyethane from dichloroethane in high yield and purity (with the intention of cleaving the methyl ether to yield the diphenol prior to cyanation), it was not possible to deprotect this group using e.g. recognised methods such as boron tribromide [17] without breaking the alkylene ether backbone.…”

Section: Introductionmentioning

confidence: 99%

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Examination of the Thermal and Thermomechanical Behavior of Novel Cyanate Ester Homopolymers and Blends with Low Coefficients of Thermal Expansion

et al. 2009

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A new four-step synthetic method is presented and applied to the preparation of three novel dicyanate monomers that comprise aryl/alkylene ether backbones with high molecular flexibility in high purity. The multi-step route involves four individual high yielding steps (each greater than 70%), thus giving an overall reaction yields for all four steps between 42% and 50% depending on the length of the backbone. The products of all steps are characterised using Fourier transform infrared spectroscopy, 1 H nuclear magnetic resonance spectroscopy, elemental analysis and melting point determination. DSC and alysis of 'uncatalysed' samples (i.e. those polymerised thermally in absence of a specific catalyst) display relatively sharp melting endotherms ranging from 66ºC to 125ºC, depending on the length (and hence flexibility of the backbone). All monomers display broad polymerisation exotherms within close agreement (87 ± 2 kJ/mol. cyanate), although the polymerisations occur in different temperature regimes. When catalysed (aluminium(III) acetylacetonate/dodecylphenol), DSC reveals that the exothermic polymerisation peaks occur at significantly lower temperatures than the uncatalysed analogues and have much narrower profiles, but tend occur in a similar temperature regime (i.e. the peak maxima fall within 205 o C -216 o C).The recorded polymerisation enthalpies for the catalysed monomers are ca. 93 ± 9.9 kJ/mol.Assessment of the thermal stabilities of the cured polycyanurates using TGA shows that the polymers lose 5% of their masses by ca. 346-366 o C, comparable with the commercial dicyanate AroCy B10, despite the greater aliphatic character. DMTA analysis is performed on the homopolymer of the commercial dicyanate AroCy B10 to validate the method and the results obtained are consistent with published data. The T g values of the homopolymers of (4a), (4b) and (4c) are determined from the peak maxima of the loss tangent, tan δ and are found to be 221 o C (4a), 139 o C (4b), and 121 o C (4c) and fall in the expected order as the backbone chain length and hence flexibility is increased. The storage moduli at 25ºC for the binary blends are significantly lower than the respective homopolymers, but the reduction in E' over the temperature range 25ºC to 200ºC is significantly improved compared with AroCy B10. When combined with AroCy B10, binary blends showed a reduction in CTE of up to 12 ppm/°C while maintaining the same value of T g .

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Examination of the Thermal and Thermomechanical Behavior of Novel Cyanate Ester Homopolymers and Blends with Low Coefficients of Thermal Expansion

et al. 2009

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“…The methyl ether of 13c,d is cleaved without epimerization using boron tribromide (30). Analysis of the product by 'H and ' H nmr spectroscopy showed that the dideuterated 2S,3~-[2,3-'H~] serine (14c) and the trideuterated 2s-[2,3,3-'H3] serine ( 1 4 4 are formed in a 2:3 ratio by the hydrogenation procedure.…”

Section: Resultsmentioning

confidence: 99%

Mechanism of formation of serine β-lactones by Mitsunobu cyclization: synthesis and use of L-serine stereospecifically labelled with deuterium at C-3

Ramer¹,

Moore²,

Vederas³

1986

Can. J. Chem.

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. VEDERAS. Can. J. Chem. 64, 706 (1986).The ring closure of N-benzyloxycarbonyl-L-serine (1) under Mitsunobu conditions (Ph3P, dimethyl azodicarboxylate, -78°C) to give the corresponding p;lactone (2) is shown by deuterium and oxygen-18 labelling studies to proceed by hydroxy group activation, in contrast to analogous cyclizations of more hindered P-hydroxy acids, which usually occur by carboxy group activation. Samples of 1 stereospecifically labelled with deuterium at C-3 were prepared by hydrogenation of (2)-2-acetamido-3-methoxyacrylic acid (9) with deuterium, followed by selective Acylase I deacetylation of the 2 s isomer, removal of the protecting groups, and N-acylation of the resulting L-serine with benzyl chloroformate. Mitsunobu cyclizations of this 3R deuterated N-acyl serine, of the [hydroxy-'80] analog l g , and of the [ c a r b~x~- '~O ] derivative If show that lactonization occurs with inversion of configuration at C-3, loss of the hydroxy oxygen, and retention of the carboxy oxygens. Similar labelling experiments demonstrate that aqueous sodium hydroxide opens the p-lactone ring by exclusive attack at the carbonyl to regenerate 1 , whereas acidic hydrolysis proceeds primarily by attack of water at the C-3 methylene group of 2. This information allows interconversion of L-serines that are stereospecifically labelled at C-3 with hydrogen isotopes and affords access to other labelled P-substituted alanines. SHAWN E. RAMER, RICHARD N. MOORE et JOHN C. VEDERAS. Can. J. Chem. 64,706 (1986).Faisant appel a des etudes par marquage au deuterium et a l'oxygkne-18, on a dCmontrC que la cyclisation de la N-benzyloxycarbonyl L-strine (I), dans des conditions de Mitsunobu (Ph3P, azodicarboxylate de dimethyle, -7g°C), qui conduit h la formation de la p-lactone corespondante se produit par le biais d'une activation du groupement hydroxyle; ceci est en opposition avec ce qui se produit lors de cyclisations analogues d'acides P-hydroxyles plus empCchCs qui se produisent habituellement par le biais d'une activation du groupement carboxyle. On a prtpart des tchantillons de 1 marques sttr6os@cifiquement par du deuterium en C-3 en proctdant a une hydrogenation de l'acide acktamido-2 methyoxy-3 acryliques-(2) (9) avec du deuterium suivie d'une deacetylation stlective de l'isomkre 2-(S) par 1'Acylase I, de l'enlkvement des groupes protecteurs et finalement d'une N-acylation de la L-strine qui en rCsulte par du chloroformate de benzyle. Les cyclisations, selon Mitsunobu, de cette N-acyl sCrine deutkrte en 3(R), de son analogue l g portant un hydroxyle "0 et du derive lf portant un carboxyle ''0 demontrent que la lactonisation se produit avec une inversion de configuration en C-3, avec une perte d'oxygkne de l'hydroxyle et avec retention des oxygknes des groupements carboxyles. Des experiences semblables de marquage ont permis de dkmontrer que, sous l'influence de l'hydroxyde de sodium aqueux, le cycle de la p-lactone s'ouvre par une attaque qui se produit exclusivement au niveau du groupement carbonyle pour regentrer l...

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“…Accordingly, demethylation of 22c occurred in a stepwise manner, and p-methoxyphenol was isolated. 25,26 3.3 Deprotection of alkyl aryl ethers AlI 3 was applied in deprotection of phenolic ethers to afford several phenol intermediates, as depicted in scheme 2. Demethylation of 24 with AlI 3 afforded 2-formyl-6-naphthol (25) in almost quantitative yield (Scheme 2A).…”

Section: Solvent Effectsmentioning

confidence: 99%

Application of aluminum triiodide in organic synthesis

Tian¹,

Sang²

2015

Arkivoc

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The multifaceted reactivity of aluminum triiodide (AlI 3 ) is reviewed. The oxophilic character of the Lewis acid enables the formation of coordination complexes with esters, ethers, oxiranes, diols, Noxides, and sulfoxides that decompose spontaneously to afford acids, alcohols and olefins via ester and ether cleavage, deoxygenation of oxiranes, and deoxydehydration of diols, respectively. As an iodide ion source and hydrogen iodide precursor, the reagent allows iodination and reduction of Noxides, sulfoxides and azides as well as hydroiodination of alkenes and alkynes. Aluminum enolates, generated by treatment of -haloketones with AlI 3 , provide accesses to -hydroxy ketones, 1,5-diones, and β-iodo Morita-Baylis-Hillman esters.

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Cleavage of Ethers

Abstract: B. The mechanism of the cleavage of ethers by anhydrous hydrogen halides.. . C. Further descriptive chemistry of cleavage by hydrogen halides.. .

Cited by 420 publications

References 83 publications

Examination of the Thermal and Thermomechanical Behavior of Novel Cyanate Ester Homopolymers and Blends with Low Coefficients of Thermal Expansion

Examination of the Thermal and Thermomechanical Behavior of Novel Cyanate Ester Homopolymers and Blends with Low Coefficients of Thermal Expansion

Mechanism of formation of serine β-lactones by Mitsunobu cyclization: synthesis and use of L-serine stereospecifically labelled with deuterium at C-3

Application of aluminum triiodide in organic synthesis

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