13466-40-5Relevant articles and documents
Electronic absorption and fluorescence properties of 2,5-diarylidene-cyclopentanones
Connors, Robert E.,Ucak-Astarlioglu, Mine G.
, p. 7684 - 7691 (2003)
Spectroscopic properties for a series of 2,5-diarylidene-cyclopentanones are reported. Electronic absorption and fluorescence spectra have been measured for the all-E configurations of 2,5-dibenzylidene-cyclopentanone (1), 2,5-bis-(3-phenyl-allylidene)-cyclopentanone (2), and 2,5-bis-(5-phenyl-penta-2,4-dienylidene)-cyclopentanone (3). The absorption spectra have been assigned with the aid of INDO/S calculations. Molecular structures used for the INDO/S calculations were computed with the PM3 Hamiltonian. Agreement between absorption spectra obtained in cyclohexane at room temperature and the theoretical predictions is good. For 1, 2, and 3 the general features of the spectra are similar. The transition to S1 (weak) is assigned as n → π* (A2 ← A1), to S2 (strong) as π → π* (B2 ← A1), and to S3 (moderate) as π → π* (A1 ← A1). The energy gap between S1 and S2 is seen to decrease as the length of the polyene chain increases in going from 1 to 3. Fluorescence is not observed for 1 in any of the solvents studied (protic and aprotic). Fluorescence is observed for 2 in protic solvents only. For 3, fluorescence is observed in a number of protic and aprotic solvents. Solvents which are able to induce fluorescence are believed to do so by inverting the order of 1(nπ*) and 1(ππ*) states. The influence of hydrogen bonding on the excitation spectra of 2 and 3 is discussed. Solvent-induced shifts in the absorption and fluorescence spectra of 3 in combination with the PM3 calculated ground-state dipole moment (2.8 D) are used to determine the excited-state dipole moment of 3 (6.4 D/protic solvents; 6.6 D/aprotic solvents). Fluorescence quantum yields in different solvents for 3 vary as the fluorescence maxima shift in these solvents, going through a maximum in the mid-frequency range. The variation in quantum yields with different solvents is primarily attributed to changes in the nonradiative rate of decay from S1. Excitation, polarized excitation, and fluorescence spectra have been measured for 2 and 3 at 77 K in ethanol/ methanol glass. Vibronic features not observed in the broad spectra obtained in alcohols at room temperature become clearly resolved at 77 K. Evidence is provided that indicates that 2 and 3 undergo excited-state proton-transfer reactions in acetic acid at room temperature.
Addition of carbon nucleophiles to aldehyde tosylhydrazones of aromatic and heteroaromatic-compounds: Total synthesis of piperine and its analogs
Chandrasekhar,Venkat Reddy,Srinivasa Reddy,Ramarao
, p. 2667 - 2670 (2000)
Addition of carbon nucleophiles to aldehyde tosylhydrazones of aromatic and heteroaromatic compounds is reported. New observations have been made wherein alkylative reduction is observed in some cases whereas alkylative fragmentation is noticed in others. These findings are exploited in the synthesis of the useful alkaloid piperine and its analogs. (C) 2000 Elsevier Science Ltd.
Derives silyles issus d'aldimines α,β-insaturees: preparations et applications en synthese
Bellassoued, M.,Majidi, A.
, p. C7 - C8 (1993)
The preparation of silylated N-tert-butyl α,β-unsaturated aldimines is reported.The disilylated reagent 3a derived from crotonaldimine is used for the conversion of aromatic aldehydes into conjugated dienals in one-pot reaction.
Aldehydes α-silyles: preparation et properties nouvelles
Duhamel, L.,Gralak, J.,Ngono, B.
, p. C4 - C6 (1989)
t-Butyldimethylsilyl acetaldehyde (3) is obtained from the hydrolysis of the (Z)-β-silylenoxysilane (2), prepared from (Z)-1-bromo-2-(trimethylsiloxy)ethylene by reaction with t-butyllithium followed by condensation with t-butyldimethylsilyl triflate.The lithium enolate of aldehyde 3 is prepared direct by reaction with lithium diisopropylamide or lithium hexamethyldisilazane; its condensation with trimethylchlorosilane leads to the (E)-β-silylenoxysilane (2) and with aldehydes, to α,β-ethylenic aldehydes (4).
Application of (2E,4E)-5-bromo-2,4-pentadienal in palladium catalyzed cross-coupling: Easy access to (2E,4E)-2,4-dienals
Vicart, Nicolas,Castet-Caillabet, Dominique,Ramondenc, Yvan,Plé, Gérard,Duhamel, Lucette
, p. 411 - 412 (1998)
Palladium catalyzed cross-coupling reactions of (2E,4E)-5-bromo-2,4-pentadienal 1 with organozinc reagents gives an easy access to the corresponding (2E,4E)-2,4-dienals. The improved preparation of all trans 1 by isomerization of its (2E,4Z) isomer is reported.
Sato et al.
, p. 8281 (1976)
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Yamamoto,K. et al.
, p. 713 - 716 (1979)
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One-Pot Preparation of (E)-α,β-Unsaturated Aldehydes by a Julia-Kocienski Reaction of 2,2-Dimethoxyethyl PT Sulfone Followed by Acid Hydrolysis
Ando, Kaori,Watanabe, Haruka,Zhu, Xiaoxian
, p. 6969 - 6973 (2021/05/06)
(E)-α,β-Unsaturated aldehydes were synthesized by the Julia-Kocienski reaction of 2,2-dimethoxyethyl 1-phenyl-1H-tetrazol-5-yl (PT) sulfone 3 with various aldehydes, followed by acid hydrolysis. The reaction could be carried out in one pot, and various (E)-α,β-unsaturated aldehydes were obtained in a short time and with high yields.
Enantioselective Organocatalytic Synthesis of 1,2,3-Trisubstituted Cyclopentanes
?otolová, Martina,Kamlar, Martin,Reme?, Marek,Géant, Pierre-Yves,Císa?ová, Ivana,?tícha, Martin,Vesely, Jan
, p. 5080 - 5089 (2021/09/30)
An organocatalytic asymmetric domino Michael/α-alkylation reaction between enals and non-stabilized alkyl halides has been developed. Chiral secondary amine catalyzed cyclization reaction of 1-bromo-3-nitropropane with α,β-unsaturated aldehydes provides 1,2,3-trisubstituted cyclopentane carbaldehydes with high diastereo- (dr up to 8 : 1) and enantioselectivities (ee up to 96 %).
