143103-67-7Relevant academic research and scientific papers
Solid phase behavior in the chiral systems of various 2-hydroxy-2-phenylacetic acid (mandelic acid) derivatives
Von Langermann, Jan,Temmel, Erik,Seidel-Morgenstern, Andreas,Lorenz, Heike
, p. 721 - 728 (2015/03/30)
The solid phase behavior of a series of monosubstituted F-, Cl-, Br-, I-, and CH3- and two 2,4-halogen-disubstituted 2-hydroxy-2-phenylacetic acid (mandelic acid) derivatives was investigated. The study includes detailed information about melting temperature, melting enthalpy, X-ray diffraction data, as well as selected binary phase diagrams of the respective chiral systems. Aside from the known metastable conglomerate 2-chloromandelic acid, evidence for two more metastable conglomerates was found.
Relationships between the racemic structures of substituted mandelic acids containing 8- and 10-membered hydrogen bonded dimer rings
Coles,Ellis,Leung,Sarson,Threlfall,Tizzard
, p. 10816 - 10823 (2015/02/19)
The structures of 27 monosubstituted mandelic acids, including several of their polymorphs, plus unsubstituted mandelic acid itself (two polymorphs) are investigated for structural similarity. The results, presented pictorially as a structural relationship plot, show that rather more structures are built up from the carboxyl-chain hydroxyl hydrogen bonded dimer than from the conventional carboxylic acid dimer. The results show how all the structures are related and, based on the two types of dimer, the degree of similarity that they possess. Some structures with Z′ > 1 contain both sorts of dimers and there are many examples of isostructural sets within the structures so far determined. We also present an example where analysing similarity in related families of structures highlights a structure that should be present and which has indeed then proceeded to be synthesised and determined.
Enantioselective cyanosilylation of aldehydes catalyzed by novel camphor derived Schiff bases-titanium(IV) complexes
B?ocka, Ewelina,Bosiak, Mariusz J.,We?niak, Miros?aw,Ludwiczak, Agnieszka,Wojtczak, Andrzej
, p. 554 - 562 (2014/05/06)
Five tridentate Schiff bases have been prepared from (1R,2S,3R,4S)-3-amino- 1,7,7-trimethylbicyclo[2.2.1]heptan-2-ol and salicylaldehydes. X-ray structure investigation revealed differences in their molecular conformation, and their titanium(IV) complexes
Enzymatic kinetic resolution of racemic cyanohydrins via enantioselective acylation
Xu, Qing,Xie, Yongli,Geng, Xiaohong,Chen, Peiran
supporting information; experimental part, p. 624 - 630 (2010/09/07)
Enzymatic kinetic resolution of a series of aromatic and aliphatic cyanohydrins in organic media has been investigated. The behavior of potential lipases, molecular sieves, acyl reagent, reaction temperature, and organic solvents on the kinetic resolution was studied. The influence of substrate structure, steric, and electronic nature and position of the aryl substituent on the enantioselectivity was discussed. Under the optimized reaction conditions, good enantioselectivity could be achieved for most of the investigated compounds. Specifically, substrates 1a, 1c, 1d, 1f, 1u could be resolved with the kinetic enantiomer ratio (E) higher than 200.
Kinetic resolution of cyanohydrins via enantioselective acylation catalyzed by lipase PS-30
Xu, Qing,Geng, Xiaohong,Chen, Peiran
supporting information; body text, p. 6440 - 6441 (2009/04/06)
By using lipase PS-30 as catalyst, the kinetic resolution of a series of racemic cyanohydrins has been achieved via enantioselective acylation. The values of kinetic enantiomeric ratio (E) reached up to 314. Substituent effect is also briefly discussed.
α-Imino and α-oximino carbocations. A comparison with α-carbonyl and α-thiocarbonyl carbocations
Creary, Xavier,Wang, You-Xiong,Jiang, Ziqi
, p. 3044 - 3053 (2007/10/02)
The σ+ values for the groups m-CH=N-t-Bu and p-CH=N-t-Bu have been determined to be 0.16 and 0.078, respectively. The CH=N-t-Bu group is therefore cation-destabilizing relative to hydrogen when placed in the meta position of a cumyl cation. Although the p-CH=N-t-Bu group is still cation-destabilizing, the effect is reduced by a competing resonance effect when the imino group is placed in the para position. However, when attached directly to a cationic center, this imino group enhances rates relative to α-H. This is interpreted in terms of a cation-stabilizing conjugative effect. The σ+ value of the p-oximino group, p-CH=NOCH3, is -0.03 and indicates that a cation-stabilizing conjugative effect can essentially offset the inductive effect of this electron-withdrawing substituent in a cumyl cation. However, when attached directly to a developing cationic center, this oximino group greatly enhances cation formation rates relative to hydrogen. This group is even more cation-stabilizing than the methyl group. Studies on systems of type ArCH(OMs)C(NOCH3)Ph, where the oximino group can be syn or anti to the developing cationic center, indicate the existence of isomeric α-oximino cations, with the anti cations forming faster than the syn cations. Computational studies at the MP2/6-31G** level support the idea of extensive conjugative stabilization of α-oximino cations. Despite extensive mesomeric stabilization of α-oximimo cations, the primary cation +CH2CH=NOCH3 cannot be solvolytically generated since nucleophilic solvent displacement processes dominate. Stabilities of a series of cations of type +CH2X, where X is a formal electron-withdrawing group, have been evaluated by ab initia methods. Isodesmic reactions indicate a stability order of α-CHNOCH3 ～ CH=CH2 > CHNHCH3 > CHS > CHO ～ H > CN > NO2.
Structures of Racemic Monofluoro-Substituted Mandelic Acids, Their Relation to the Thermochemical Properties and an Analysis of Short Intermolecular Fluorine-Carbon Contacts
Larsen, Sine,Marthi, Katalin
, p. 373 - 381 (2007/10/02)
The structures of the three monofluoro-substituted mandelic acids (C8H7FO3, Mr=170.14) have been determined from low-temperature X-ray diffraction data . o-Fluoromandelic acid, monoclinic, P21/c, a=8.4238 (12), b=5.4766 (7), c=15.959 (2) Angstroem, β=95.962 (11)o, V=732.3 (3) Angstroem3, Z=4, Dx=1.543 g cm-3, μ=11.25 cm-1, F(000)=352, R=0.040 for 1357 contributing reflections, m.p. 388.3 (5) K. m-Fluoromandelic acid (metastable modification), monoclinic, P21/a, a=10.8657 (14), b=9.2663 (10), c=15.722 (2) Angstroem, β=107.474 (10)o, V=1509.9 (6) Angstroem3, Z=8, Dx=1.497 g cm-3, μ=10.92 cm-1, F(000)=704, R=0.048 for 2977 contributing reflections, m.p. 368.4 (5) K. p-Fluoromandelic acid, orthorhombic, Pbca, a=9.4685 (9), b=16.497 (2), c=9.7677 (8) Angstroem, V=1525.7 (5) Angstroem3, Z=8, Dx=1.481 g cm-3, μ=10.80 cm-1, F(000)=704, R=0.042 for 1489 contributing reflections, m.p. 408.9 (5) K.The results obtained from the structure determination are related to their physico-chemical properties examined by differential scanning calorimetry (DSC).The DSC measurements showed that m-fluoromandelic acid is prepared as a metastable modification.The distortions of the angles of the benzene rings observed in the three acids are identical, within experimental error, to those predicted from the sum of the substituent effects.Hydrogen bonds are important for the crystal packing in all these structures, and in addition very short distances are observed in the ortho- and para-substituted acids between the F atom and the C atom of the carboxylic acid group.Semi-empirical calculations indicated that these short distances correspond to attractive electrostatic interactions.The carbon-fluorine interactions were also elucidated by a search in the Cambridge Structural Database. m-Fluoromandelic acid has the lowest melting enthalpy and entropy.This is consistent with the lack of C...F interactions and the presence of two molecules per asymmetric unit in this compound.The ortho and para acids which have similar intermolecular interactions have similar melting enthalpies and entropies, which are higher than those observed in m-fluoromandelic acid.
Optically Active Amines. 36. Application of the Benzene Chirality Rule to Ring-Substituted Mandelic Acids
Colon, Diana F.,Pickard, Simeon T.,Smith, Howard E.
, p. 2322 - 2326 (2007/10/02)
The positive sign of the 1Lb Cotton effects (CEs) from about 250 to 270 nm in the circular dichroism (CD) spectrum of (R)-mandelic acid and its sodium salt is determined by vibronic borrowing from allowed transitions at shorter wavelength.On ring substitution, transition moments are induced in the benzene ring bonds adjacent to the attachment bond of the chiral group, resulting in enhanced coupling of the 1Lb transition with the chiral group.The sign of the 1Lb CEs for a ring-substituted (R)-mandelic acid may be the same or opposite to that of (R)-mandelic acid, but the sign of its 1Lb CEs can often be correlated wit h its absolute configuration provided the ring position of the substituent and its spectroscopic moment is taken into account.
Enzymatic Preparation of Optically Active Cyanohydrin Acetates
Almsick, Andreas van,Buddrus, Joachim,Hoenicke-Schmidt, Petra,Laumen, Kurt,Schneider, Manfred P.
, p. 1391 - 1393 (2007/10/02)
A series of cyanohydrin acetates (1)-(47) of widely varying structures, potential chiral building blocks for numerous synthetic applications, has been prepared in good chemical and often high optical yields by enzymatic hydrolysis of their racemic acetates in the presence of an ester hydrolase from Pseudomonas sp.
