Thermisches Verhalten von Cyclopropa[<i>c</i>]chromenen

Hug, R.; Fráter, Georg; Hansen, H.-J.; Schmid, Hans

doi:10.1002/hlca.19710540130

Cited by 28 publications

(5 citation statements)

References 24 publications

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“…Cyclic ether 179 undergoes rearrangement upon heating at 250 °C to provide 182. 95 Higher temperature was required for the conversion of anti-azotricyclic compound 183 to diene 184 than for syn compound 185; rearrangement of 185 proceeds smoothly at 121 °C to give dihydroazepine 184, whereas the rearrangement of 183 required 350 °C.96 This difference in reactivity was rationalized in terms of the ease of the formation of the ylide intermediate 186.97 Passing a hexane solution of 186 cyclopropyl ketone 187 through a column heated at 350 °C gave keto ester 188 in 79% yield via an ene-type process.98 Thermolysis of methyl ketone 189 at 175 Homo-[l,5]-sigmatropic hydrogen migration was responsible for the rearrangement of 199 to a mixture of 200 alkylvinylcyclopropanes and has been shown to be reversible. 60 The thermal rearrangement of oxaspiropentanes 205 to cyclobutanones 206 is well-known and its application has been reviewed elsewhere.103…”

Section: Miscellaneous Thermal Fissionmentioning

confidence: 99%

Use of cyclopropanes and their derivatives in organic synthesis

Wong¹,

Hon²,

Tse³

et al. 1989

Chem. Rev.

951

315

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Section: Miscellaneous Thermal Fissionmentioning

confidence: 99%

Use of cyclopropanes and their derivatives in organic synthesis

Wong¹,

Hon²,

Tse³

et al. 1989

Chem. Rev.

951

315

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“…Enthalpy of curing was 190 J g −1 . The mechanism of thermal cyclization of aryl propargyl ethers to chromenes by a Sigmatropic rearrangement (Claisen rearrangement) is well established . Chromenes undergo thermal homopolymerization to poly(chromenes) .…”

Section: Resultsmentioning

confidence: 99%

“…The mechanism of thermal cyclization of aryl propargyl ethers to chromenes by a Sigmatropic rearrangement (Claisen rearrangement) is well established. [26][27][28] Chromenes undergo thermal homopolymerization to poly(chromenes). [28][29][30][31] In the present case also, similar reaction prevails where the propargyl ether units in PEEK-PR undergoes Claisen rearrangement to the corresponding bischromenes and further polymerization to poly(chromenes).…”

Section: Characterizationmentioning

confidence: 99%

Poly(ether ether ketone)‐bischromenes: Synthesis, characterization, and influence on thermal, mechanical, and thermo mechanical properties of epoxy resin

Karthikeyan

Mathew

Robert

2019

Polymers for Advanced Techs

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Poly(ether ether ketone) s with terminal propargyl groups (PEEK‐PR) were synthesized from hydroxyl terminated PEEK (PEEKTOH) and characterized. The heat‐triggered polymerization of PEEK‐PR to poly bischromenes having PEEK backbone was confirmed by Fourier transform infrared spectroscopy and differential scanning calorimetric studies. PEEK‐PR was blended with a bisphenol based epoxy resin‐diamino diphenylsulphone system in different proportions and cured to form PEEK‐bischromene‐interpenetrated‐epoxy‐amine networks. Tensile strength and elongation of the cured blends increased up to 10‐phr loading of PEEK‐PR and then declined. Tensile moduli of all formulations were comparable. Fracture toughness increased by a maximum of 33%, and the fractured surface morphology showed a ductile fracture. The blends exhibited slightly lower glass transition temperature to that of the neat epoxy‐amine system. A reference sample of epoxy‐amine was processed with the optimum loading of the precursor polymer, PEEKTOH, and compared its properties with the PEEK‐PR incorporated epoxy systems. In this way, it is found that the incorporation of addition curable propargylated PEEK increases the strength characteristics with adequate thermal stability and fracture toughness for high‐performance structural applications.

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“…It is known that propargyl ether substituted phenols undergo Claisen rearrangement on heating to give 2‐H chromenes 17. The uncatalysed rearrangement is normally effected at high temperature and so is always accompanied by thermal polymerization of the formed chromene.…”

Section: Resultsmentioning

confidence: 99%

Addition‐cure phenolic resins based on propargyl ether functional novolacs: synthesis, curing and properties

Bindu

Nair

Ninan

2001

Polymer International

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Thermosetting phenolic resins, bearing varying extents of propargyl ether groups (PN resins), have been synthesized by the Williamson reaction of a novolac with propargyl bromide and the products characterized. The resin precursors were cured through Claisen rearrangement of the propargyl ether groups and thermal polymerization. The activation energy for thermal cure is substantially lower than that of model bispropargyl ether compounds but is quite independent of the degree of functionalization. The isothermal cure pro®le, extrapolated from non-isothermal DSC kinetics studies is consistent with the results from DMA studies. The mechanical properties of glass composites of the resins, of varying propargyl contents, reveal good consolidation of the interphases, evident from the initial gain in both interlaminar shear strength (ILSS) and¯exural strength. The bene®ts of better resin±reinforcement interactions are not retained on crosslinking the resin further, wherein the composite fails by a combination of ®bre debonding and brittle fracture of the matrix. Although the resins show better thermal stability than cured resoles, a higher extent of propargylation is detrimental for the thermal stability. Resins with moderate propargylation show good mechanical and thermal properties.

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Thermisches Verhalten von Cyclopropa[c]chromenen

Cited by 28 publications

References 24 publications

Use of cyclopropanes and their derivatives in organic synthesis

Use of cyclopropanes and their derivatives in organic synthesis

Poly(ether ether ketone)‐bischromenes: Synthesis, characterization, and influence on thermal, mechanical, and thermo mechanical properties of epoxy resin

Addition‐cure phenolic resins based on propargyl ether functional novolacs: synthesis, curing and properties

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