1657-65-4Relevant academic research and scientific papers
Surface enhanced Raman spectroscopic (SERS) behavior of substituted propenoic acids used in heterogeneous catalytic asymmetric hydrogenation
Firkala, Tams,Tlas, Emlia,Kristyn, Sndor,Sz?ll'si, Gy?rgy,Drotr, Eszter,Mink, Jnos,Mihly, Judith
, p. 1102 - 1109 (2016/01/26)
The strength and geometry of adsorption of substituted propenoic acids on silver surface were studied by means of surface enhanced Raman spectroscopy (SERS) using silver sol. Based on their SERS behavior, two classes of phenylpropenoic acids studied were distinguished. The first class of propenoic acids (atropic acid, (E)-2,3-diphenylpropenoic acid, (E)-2-(2-methoxyphenyl)-3-phenylpropenoic acid, (E)-2,3-di-(4-methoxyphenyl)phenylpropenoic acid and (E)-2-(2-methoxyphenyl)-3-(4-fluorophenyl)propenoic acid) has shown strong charge transfer (CT) effect. We suggest bidentate carboxyl bonded species based on the SERS enhanced bands of νCOO- around 1394 cm-1 and νC-C of the -C-COO- moiety at 951 cm-1. In these series the plane of the α-phenyl group (γCH out-of-plane vibrations at 850-700 cm-1) is almost parallel to the silver surface, while the β-phenyl group is in tilted position depending on the type and the position of substituent(s) showing strong SERS enhanced bands of νCC + βCH (in-plane mode) at 1075 cm-1, νCC (ring breathing mode, in-plane) at 1000 cm-1 and γCCC (out-of-plane mode) around 401 cm-1. The other class of propenoic acids (cinnamic acid, (E)-2-phenyl-3-(4-methoxyphenyl)propenoic acid) has shown weak electromagnetic (EM) enhancement (CC bands is enhanced in cinnamic acid). In this case no significant carboxyl enhancement was observed, so we suggest that adsorbed species lie parallel to the surface. The two types of adsorption can be related to the dissociation ability of the carboxylic group. In the first case the carboxylic H dissociates, while in the second case it does not, as indicated also by the characteristic νCO band at 1686 cm-1 in the FT-Raman spectra of methanolic solutions.
Reactions of chlorine substituted (E)-2,3-diphenylpropenoic acids over cinchonidine-modified Pd: Enantioselective hydrogenation versus hydrodechlorination
Szllsi, Gy?rgy,Hermán, Beáta,Szabados, Erika,Fül?p, Ferenc,Bartók, Mihály
experimental part, p. 28 - 36 (2011/02/24)
The effect of the chlorine position on the C-Cl bond hydrogenolysis and the enantioselective hydrogenation of Cl substituted (E)-2,3-diphenylpropenoic acid derivatives has been studied over cinchonidine-modified Pd/Al2O 3. In contrast to the fast hydrodechlorination of the β-phenyl-para-Cl substituted acids the Cl on the α-phenyl ring was barely hydrogenolized. These observations were interpreted by the different arrangements of the two phenyl rings on the surface, with the α- and β-phenyl rings adsorbed tilted and parallel, respectively. The results confirmed the beneficial effect of the α-phenyl-ortho-substituents on the chiral discrimination, thus the 2,3-diphenylpropionic acids substituted by Cl on the α-phenyl ring could be prepared in good yields and optical purities. The conclusions were used for the rational design of an acid, i.e. (E)-2-(2-methoxyphenyl)-3-(3,4-difluorophenyl)propenoic acid, which afforded the best optical purity (ee up to 95% at 295 K) described until now in this heterogeneous system.
Synthesis of E- and Z-o-methoxy-substituted 2,3-diphenyl propenoic acids and its methyl esters
Felfoeldi, Karoly,Sutyinszky, Maria,Nagy, Nora,Palinko, Istvan
, p. 1543 - 1553 (2007/10/03)
A series of stereoisomeric o-methoxy-substituted 2,3-diphenyl propenoic acids and their methyl esters have been synthesized. The E isomers were prepared by a modified Perkin condensation (substituted benzaldehyde, phenylacetic acid, Et3N/acetic anhydride). The difficult to access Z isomers were obtained conveniently in good yields when the appropriate coumarin derivatives were allowed to react with KOH and CH3I in DMSO.
Reactions of carbonyl compounds in basic solutions. Part 34. The mechanism of the base-catalysed ring fission of 2,3-diphenylcycloprop-2-en-1-one
Bowden, Keith,Burgess, Emma J.
, p. 1594 - 1600 (2007/10/03)
The rate coefficients for the base-catalysed ring fission of a series of 2-phenyl-3-(2-, 3-or 4-substituted phenyllcycloprop-2-en-1-ones to give the corresponding (E)-2,3-diphenylacrylic acids have heen determined in water at 30.0 °C, as well as for the unsubstituted compound at 40.0, 50.0 and 60.0 °C. The effects of meta-and para-substituents on the rates have been correlated using the Hammett equation to give a reaction constant, p, equal to ca 1.2 at 30 °C. For the unsubstituted compound, the activation parameters have been calculated and the kinetic solvent isotope effect has been studied. The effects of ortho-substituents on the rates appear to be mainly polar, rather than steric, in origin. The evidence indicates a mechanistic pathway which proceeds by addition of hydroxide anion to the ketone, which is rate-determining. The adduct suffers ring fission to give the final product via a carbanionic intermediate.
Protonation and ring closure of stereoisomeric α-substituted cinnamic acids in superacidic media studied by 13C NMR spectroscopy and computations
Palinko, Istvan,Burrichter, Arwed,Rasul, Golam,Toeroek, Bela,Prakash, G. K. Surya,Olah, George A.
, p. 379 - 385 (2007/10/03)
Five α-substituted cinnamic acids [(E)- and (Z)-2,3-diphenyl-, (E)- and (Z)-3-(2-methoxyphenyI)-2-phenyl- and (E)-2-(2-methoxyphenyl)-3-phenyl-propenoic acids] have been protonated in fluorosulfonic acid at -78°C. Protonation of the carboxylic group and a second protonation on the methoxy group at -78°C or the ring bearing the methoxy group at 0°C have been observed by 13C NMR spectroscopy. Upon protonation (Z)-α-phenylcinnamic acid is transformed to a protonated indenol derivative. Dehydrative ring closure begins at -78°C and goes to completion at 0°C. Similar transformations of the other studied Z-acid are suppressed by the deactivating effect of the protonated methoxy group. Only protonation has been observed for the E-acids at -78°C as well as 0°lculations at the HF/3-21G level provide the equilibrium structures of the corresponding cations. Results of IGLO/13C NMR shift calculations are in good agreement with the experimental findings.
ACID CATALYZED ISOMERIZATION OF Z-α-PHENYLCINNAMIC ACIDS AND THEIR CONVERSION TO ISOMERIC ISOAURONES
Gadre, S. Y.,Marathe, K. G.
, p. 1015 - 1028 (2007/10/02)
E(4') and Z(4)-α-phenylcinnamic acids were synthesized.These were been converted into isoaurones.The stereochemistry of these were determined by 1H NMR and Lanthanide induced shift (LIS) studies.
