The photocyclisation of stilbene analogues

Blackburn, E. V.; Timmons, Cody

doi:10.1039/qr9692300482

Cited by 108 publications

(42 citation statements)

References 1 publication

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“…By plasma application, the concentration of layer-composing species is enhanced. However, due to the lower electron density with increasing pressure and the decreasing electron temperature, the rate of layer formation decays exponentially [36], but remains above the CVD branch ( Figure 7; further discussion in Section 3.3).…”

Section: Plasma Cleavagementioning

confidence: 99%

Correlation of Growth and Surface Properties of Poly(\(p\)-xylylenes) to Reaction Conditions

2015

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Parylene, a non-critical, non-toxic layer material, which is not only a candidate for low-K dielectrics, but also well suited for long-term applications in the human body, has been deposited by (plasma-enhanced) chemical vapor deposition of the monomeric species. To that end, a specially-designed reactor exhibiting a cracker tube at its entrance, which serves as the upstream control, and a cooling trap in front of the downstream control has been applied. The process of polymerization has been traced and is explained by evaporating the dimeric species followed by dissociation in the cracker at elevated temperatures and, eventually, to the coating of the polymeric film in terms of thermodynamics. Alternatively, the process of dissociation has been accomplished applying a microwave plasma. In both cases, the monomerization is controlled by mass spectrometry. The window for surface polymerization could be clearly defined in terms of a factor of dilution by an inert gas for the chemical vapor deposition (CVD) case and in the case of plasma-enhanced chemical vapor deposition (PECVD), additionally by the power density. The characterization of the layer parameters has been carried out by several analytical tools: scanning electron microscopy and atomic force microscopy to determine the surface roughness and density and depth of voids in the film, which influence the layer capacitance and deteriorate the breakdown voltage, a bulk property. The main issue is the conduct against liquids between the two borders' hydrophilic and hydrophobic conduct, but also the super-hydrophobic character, which is the condition for the Lotus effect. The surface tension has been evaluated by contact angle measurements. Fourier-transform infrared spectroscopy has proven the conservation of all of the functional groups during polymerization.

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Section: Plasma Cleavagementioning

confidence: 99%

Correlation of Growth and Surface Properties of Poly(\(p\)-xylylenes) to Reaction Conditions

2015

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“…39,40 The multistep conversion comprises isomerization of E-stilbenes to Z-stilbenes, followed by cyclization of intermediate radicals to dihydrophenanthrenes that are irreversibly dehydrogenated to phenanthrenes in the presence of oxidants. 37 The stilbenes 84-87 required for our investigation were prepared by Wittig reaction using the procedure of The preferential formation of the less hindered regioisomer has also been observed in hydroxylated precursors.…”

Section: Photocyclizationmentioning

confidence: 99%

“…Several regioisomers can theoretically be formed in the reaction of methoxybenzoquinone (39) with the styrenes 23-37. In practice, the number is reduced to two isomers because the addition occurs only at the non-substituted ethylene linkage of the benzoquinone, probably for steric as well as electronic reasons.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and electrochemistry of annoquinone-A, cypripedin methyl ether, denbinobin and related 1,4-phenanthrenequinones

Krohn¹,

Loock²,

Paavilainen³

et al. 2001

Arkivoc

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The natural product annoquinone-A (1), the 1,4-phenanthrenequinones 41-75 and the 9,10-dihydro-1,4-phenanthrenequinones 76-81 were prepared by Diels-Alder reaction of the styrenes 23-37 with the benzoquinones 38-40. The sterically hindered 5-methoxy compounds, which adopt a twisted conformation as shown by X-ray analysis, are only formed in trace amounts or as the less hindered 9,10-dihydro-1,4-phenanthrenequinones 76-81. The twisted conformation also leads to characteristic changes in the NMR spectra and the redox potential. Reaction of methoxybenzoquinone with styrenes preferentially affords the 3-methoxy-1,4-phenanthrenequinones. Selective ether cleavage of the 5-methoxy group in 60 leads to the natural product denbinobine (3). Small amounts of C-9 hydroxylated compounds (57, 66, 68, 73, and 75) were also formed in the Diels-Alder reactions. In an alternative synthesis, using the photocylization of the stilbenes 84-87 followed by CAN oxidation, the 1,4-phenanthrenequinones 45, 51, 59 [methyl ether of cyprepidine (2)

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“…ref. 21). Also related to the conversion 30, 31 --+ 32, 33, is the thermal cyclization of pentadienal oximes into pyridines 22 .…”

Section: Photolysis Of Benztriazolesmentioning

confidence: 99%

Photochemistry of some heterocyclic systems

Claus¹,

Doppler²,

Gakis³

et al. 1973

Pure and Applied Chemistry

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The photocyclisation of stilbene analogues

Cited by 108 publications

References 1 publication

Correlation of Growth and Surface Properties of Poly(\(p\)-xylylenes) to Reaction Conditions

Correlation of Growth and Surface Properties of Poly(\(p\)-xylylenes) to Reaction Conditions

Synthesis and electrochemistry of annoquinone-A, cypripedin methyl ether, denbinobin and related 1,4-phenanthrenequinones

Photochemistry of some heterocyclic systems

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