24815-58-5Relevant academic research and scientific papers
Excited-State Properties of trans-1-(9-Anthryl)-2-(4-R-phenyl)ethylenes with Electron-Donating and -Accepting Substituents (R=N(CH3)2, OCH3, CH3, Br, CN, and NO2)
Sun, Licheng,Goerner, Helmut
, p. 11186 - 11193 (2007/10/02)
The decay pathways of the lowest excited singlet state (1t*) of trans-1-(9-anthryl)-2-(4-R-phenyl)ethylenes (trans-R-StAs, where R=N(CN3)2, OCH3, CH3, Br, CN, and NO2 on the 4-position of the styryl) were studied in solution at room and low temperatures.Fluorescence lifetime (τf) and quantum yield (Φf) as well as the yield (ΦT) and spectral and kinetic properties of the lowest triplet state were determined by steady-state and transient techniques.The solvent polarity has a large effect on the Stokes shift for (H3C)2N- and O2N-StA, the two derivatives with the strongest electron-donating and -accepting substituents.The smallest changes in Φf and ΦT, in comparison with the case of parent 9-StA, are caused by the Br or CH3 groups.For O2N- and (H3C)2N-StA, and to a lesser degree for NC- and H3CO-StA, Φf and τf become significantly smaller with increasing solvent polarity.Efficient deactivation by charge transfer via an excited singlet state with essentially trans configuration (A*) is proposed for these derivatives.The 1t*->A* relaxation pathway in polar solvents is activated and competes with fluorescence and intersystem crossing.For NC-, H3CO-, and (H3C)2N-StA at room temperature trans->cis photoisomerization occurs with substantial quantum yield (Φt->c) in those solvents in which the presence of the postulated A*-state efficiency reduces fluorescence and intersystem crossing.A contribution of a triplet mechanism to trans->cis photoisomerization can be excluded throughout.A special case is O2N-StA, which exhibits virtually no photochemistry in both nonpolar and polar solvents, but Φt->c is up to 0.2 in slightly polar solvents, e.g., toluene.
A Stereoselective Synthesis of Olefins by a New Semi-stabilized Phosphonium Ylide
Gupta, K. C.,Pathak, P. K.,Saxena, B. K.,Srivastava, Nirupma
, p. 196 - 198 (2007/10/02)
A new semi-stabilized phosphonium ylide, viz. (9-anthrylmethylene)triphenylphosphorane (2) generated by the action of sodium hydride or sodamide in benzene or sodium methoxide in methanol on (9-anthrylmethyl)triphenylphosphonium bromide (1), has been reacted with substituted aromatic aldehydes (3) to give exclusively the trans-1-(9-anthryl)-2-substituted-arylethylenes (4).The variation of solvents and bases has no effect on the stereoselectivity of the reaction.The trans-geometry of 4 has been established by IR and PMR spectral data.
Effect of Bulky Size of Carbonyl Systems on Betaine Decomposition of Semi-stablized Arsonium Ylids
Gupta, K. C.,Srivastava, N.,Nigam, R. K.
, p. 802 - 803 (2007/10/02)
Reactions of substituted benzylidentriphenylarsenanes (2a-i) with 9-anthraldehyde and 9-fluorenone have been studied using benzene-sodamide, chloroform-sodium hydride and methanol-sodium ethoxide as solvent-base pairs.In all the cases olefins (5a-i and 6a-i) are formed exclusively.Variation of solvents and bases has no effect on the course of betaine decomposition formed by the nucleophilic attack of ylids on carbonyl systems.
SYNTHESIS OF DIARYLETHYLENES WITH CONDENSED RINGS BY THE WITTIG REACTION
Listvan, V. N.,Gonchar, G. V.,Rudenko, E. S.,Onishchenko, T. A.,Stasyuk, A. P.
, p. 1528 - 1533 (2007/10/02)
The Wittig reaction was used for the synthesis of diarylethylenes containing condensed naphthalene, anthracene, phenanthrene, and pyrene rings.Unlike 9-anthracenecarbaldehyde, which gives the trans isomers almost exclusively in the Wittig reaction with ar
