Welcome to the Research Articles

J. Jaime Vázquez Bravo




Name of article IP address Abstract year
Matrix Representation of Stereoisomers and New Polygonal Stereoisograms http://match.pmf.kg.ac.rs/electronic_versions/Match81/n3/match81n3_603-620.pdf A new method to find the complete set of stereoisomers of chiral molecules is presented herein. This method consists in the use of binary alphabet (0, 1) instead of the binary code (R, S), which was originally coined by Cahn-Ingold-Prelog for characterizing to tetrahedral stereogenic centers. With this change, each one of the stereoisomers of a given molecule containing n stereogenic centers can be written as a n-bit binary string and the full set of stereosiomers can be represented as a m-by-n matrix (where m is the maximum number of stereoisomers possible, m = 2n). In turn, the n-bit binary strings can be easily developed by a combinatorial technique starting from an all-zeros string (u) until ending in an all-ones string (f); in the middle there are subsets of strings with one, two…, n-1 substituted 0’s by 1’s, which are labeled as ai, bj, ck …, etc. Moreover, the numbers of strings in each subset are coincident with those ones in n-level of Pascal’s Triangle and used as coefficients of a mathematical expression that describes to the total number of stereoisomers of a molecule containing n stereogenic centers. 2019
Highly Regioselective Ring Opening of a Common N,N-Dialkylaziridinium Ion by Carboxylic Acids https://www.heterocycles.jp/newlibrary/payments/form/25414/PDFwithLinks A variety of optically active amino esters were synthesized via ring-opening reaction of (R)-1-phenyl-3-azaspiro[2.5]octan-3-ium ion derived from (R)-2-phenyl-2-(piperidin-1-yl)ethan-1-ol in a highly regioselective manner. Ring-opening reaction with carboxylates series generated in situ proceeded smoothly and with excellent yields (85-98%). 2018
Crystal structure of r-1, c-2-dibenzoyl-t-3, t-4-bis (2-nitrophenyl) cyclobutane https://scripts.iucr.org/cgi-bin/paper?ex2002 The condensation reaction of acetophenone (1-phenylethan-1-one) with 2-nitrobenzaldehyde in the molten state yielded the expected chalcone, (E)-3-(2-nitrophenyl)-1-phenylprop-2-en-1-one, and, unexpectedly, the title compound, C30H22N2O6, which results from the syn head-to-head [2 + 2] cycloaddition of the chalcone. The molecular structure of the dimer shows that the four benzene rings of the substituents are oriented in such a way that potential steric hindrance is minimized, whilst allowing some degree of intermolecular p–p interactions for crystal stabilization. In the molecule, one nitro group is disordered over two positions, with occupancies for each part of 0.876 (7) and 0.127 (7). 2017
Molecular docking studies between two palladium complexes https://www.researchgate.net/profile/Oscar_Zuniga/publication/291822126 Cis-diaminedichloroplatinum (II),[cis-(NH3) 2PtCl2], is one of the most successful anticancer compounds. In recent years the search for new drugs with antineoplastic activity has led to synthesis of palladium complexes, because of its analogy with Platinum (II). The aim in this study was to show the interaction between DNA and palladium complexes using docking studies, to elucidate the possible action mechanism of cis-[(1S, 2S)-(-)-N1, N2-bis (1-phenylethyl)-1, 2-propanodiimine] PdCl2 and cis-{(1S, 2S)-(-)-N1, N2-bis [1-(4-metilphenyl) ethyl]-1, 2-propanodiimine} PdCl2). Our results suggest a possible interaction of palladium complex and the DNA, forming a covalent bond manner similar to cisplatin. 2015
Solvent-free synthesis of ferrocenylchalcones http://sphinxsai.com/2014/ChemTech/JM14CT1_50/CT=17(138-146)JM14.pdf A series of ferrocenylmono- and dichalcone derivatives have been synthesized under solvent-free
conditions via Claisen-Schmidt condensations between aryl/ferrocenyl ketones and aryl/ferrocenyl aldehydes by
just grinding in an agate mortar. All the reactions occur in a short time with excellent yields (>85%) of
steroselective trans-conformation in the chalcones. The structures of all the compounds have been characterized
by FT-IR, 1H NMR, 13C NMR and EI-MS and elemental analyses.
Antioxidant Properties of Organostibines Against Lipid Peroxidation in Homogenized Rat Brain. https://web.a.ebscohost.com/abstract? The effect of six different synthesized organoantimony compounds viz. tris-(3-methyl-2-thienyl) stibine (1), tris-(5-chloro-2-thienyl) stibine (2), tris-(2-selenophenyl) stibine (3), chloro-bis (N, N-dimethyl-(1-ferrocenylethyl amine) Sb (III)(4), tris-(2-dimethyl aminoethyl ferrocenyl) stibine (5), 1-(2-diphenylstibine-ferrocenyl) methyldimethylamine (6) on thiobarbituric acid reactive species (TBARS) production, free radical activity in the rat brain homogenate were determined. Their antioxidant activity were compared with the quercetin, Butylated hydroxytoluene (BHT; 2,[6]-di-tert-butyl-pcresol) and a-tocopherol as reference antioxidants. All compounds showed a dose dependent inhibition on TBARS production. Tris-(5-chloro-2-thienyl) stibine (2) showed lipid peroxidation inhibition in homogenized rat’s brain, double in magnitude, than shown by tris-(3-methyl-2-thienyl) stibine (1) activity. 2013
Acoplamiento molecular y actividad antibacteriana de las tioureas (R, R)-N, N´-bis (1-ciclohexiletil) tiourea y (R, R)-N, N´-bis (1-feniletil) tiourea https://www.redalyc.org/pdf/3313/331327989004.pdf Las tioureas, son compuestos resultantes de sustituir el átomo de oxígeno de la urea (NH2CONH2) por un átomo de azufre (NH2CSNH2). Actualmente se ha visto que las tioureas presentan diversas actividades biológicas, dentro de las que se encuentra la antimicrobiana. En el presente estudio se evaluó la actividad antibacteriana mediante acoplamiento molecular entre la enzima DNA girasa (receptor) y las tioureas (R, R)-N, N-bis (1-ciclohexiletil) tiourea (CYTU1) y (R, R)-N, N-bis (1-feniletil) tiourea (CYTU2) como ligando en busca del posible mecanismo de acción de estos compuestos, los resultados muestran que existe interacción entre la enzima y ambas tioureas en el sitio activo. Por otro lado, también se evaluó la actividad antibacteriana frente a cepas de Sthapylococcus aureus, Escherichia coli y Pseudomonas fluorescens, mediante el método de microdilución en caldo con la adición de bromuro de 3-(4, 5-dimetil-2-tiazolil)-2, 5-difeniltetrazolium (MTT), como parte del ensayo de viabilidad, mostrando una disminución de la misma sólo contra las bacterias gram negativas, siendo la tiourea CYTU2 la que mostró mejor actividad antibacteriana. 2013
Synthesis and Characterization of New 1, 2-Disubstituted Ferrocenyl Bismuthines https://www.tandfonline.com/doi/abs/10.1080/15533174.2012.680162 Bismuthine Ph2BiFc containing the pendant arm 2-(Me2NCH2)- (1) on ferrocenyl ring was synthesized, and reaction of (1) with CH3I was carried out to obtain the monoammonium salt {[2-(Me3N+CH2)Fc]}BiPh2[I]- (2). Molecular structures of bismuthines (1) and (2) have been determined by X-ray crystallography. Compound (1) does not show hypervalent Bi-N interaction. New 1,2-disubstituted ferrocenyl bismuthines have been characterized by various physicochemical techniques. 2012
Synthesis, characterization and anticancer activity of new chiral Pd(II)-complexes derived from unsymmetrical α-diimine ligands https://www.sciencedirect.com/science/article/abs/pii/S0277538711003950 A set of new diastereopure unsymmetrical α-diimine ligands 2a–d derived from methylglyoxal and optically pure primary amines 1a–d afforded the new chiral Pd(II)-complexes (S,S)-3a, (S,S)-3b, (S,S)-3c, and (1S, 2S, 3S, 5R)-3d. All compounds have been characterized by IR, 1H, and 13C NMR spectroscopies along with MS-FAB+ spectrometry. The crystal and molecular structure for the complexes 3a, 3b and 3d have been fully confirmed by single-crystal X-ray studies. Likewise, complexes 3a–d have also been screened for their in vitro cytotoxicity against different classes of cancer: leukemia (K-562 CML), colon cancer (HCT-15), human breast adenocarcinoma (MCF-7), central nervous system (U-251 Glio) and prostate cancer (PC-3) cell lines. 2011
(S)-(+)-N-Benzylidene-1-(1-naphthyl) ethylamine https://scripts.iucr.org/cgi-bin/paper?LD2008 In the title chiral aldimine, C19H17N, the azomethine group is not fully conjugated with the phenyl substituent: the dihedral angle between phenyl and C*—N=C mean planes is f3 = 23.0 (2)°. Compared with the earlier DFT-B3LYP/6–31 G(d) computations from the literature, the C=N—C*—C(naphthyl) torsion angle, found at f2 = -118.0 (2)° in the X-ray structure, does not match the angle calculated for the potential minimum energy at f2 = 0°. However, this angle is close to the second potential energy minimum at f2 = -120° which is ca. 8.5 kJ mol-1 above the global energy minimum. Thus, the reported X-ray structure corresponds to the second most likely (according to DFT) conformer, allowing the existence of other polymorphs to be anticipated. 2011
Conformación molecular y estructura cristalina de una Diimina Quiral: 1, 4-BIS [(+)-(S)-(1-Feniletilimino) Metil] Beceno http://eprints.uanl.mx/9745/ La síntesis de una nueva bis-imina quiralmente pura, de fórmula C24H24N2 se llevó a cabo por síntesis directa, en ausencia de disolvente , y la caracterización estructural se realizó por difracción de Rayos X en monocristal. los grupos imino tienen la configuración E, común en aldiminas secundarias con un grupo estorboso sustituyendo el átomo de nitrógeno. 2010
(–)-(S)-N, N’-Bis [1-(1-naphthyl) ethyl] oxalamide https://scripts.iucr.org/cgi-bin/paper?JH2225 The title molecule, C26H24N2O2, displays C2 symmetry, with the molecule located on a twofold axis perpendicular to the plane of the oxalamide unit –NH—CO—CO—NH–. The oxalamide core deviates from planarity, as reflected by the O=C—C=O and N—C—C—N torsion angles of 164.3 (5) and 163.2 (5)°, respectively. The naphthyl groups are oriented toward the same face of the oxalamide mean plane and make a dihedral angle of 43.76 (8)°. This conformation is suitable for the formation of intermolecular N—H?O hydrogen bonds, giving noncentrosymmetric dimers incorporating R22(10) ring motifs. These nonbonding interactions propagate along the 61 screw axis normal to the molecular twofold axis, resulting in a single-stranded right-handed helix parallel to [001]. In the crystal, ? helices are arranged side-by-side and interact through p–p contacts between naphthyl groups. 2010
Tris-(1, 2-N, N-dimethylaminomethylferrocenyl) stibine and its heterotrimetallic complex https://www.sciencedirect.com/science/article/pii/S0022328X08004889 New tertiary chloro-bis(1,2-N,N-dimethylaminomethylferrocenyl)stibine (1) and tris-(1,2-N,N-dimethylaminomethylferrocenyl)stibine ligand (2) containing CH2NMe2 pendenant arm at the ortho-position have been synthesized. Stibine (2) reacts with PtCl42- and hetero trimetallic cis-PtCl2L (3) complex is obtained, where stibine (2) acts as a bidentate ligand. All these compounds were characterized by various physicochemical methods and their molecular structures were determined by X-ray diffraction analyses. It is to be noted that tris(1,2-aminomethylferrocenyl)stibine represents the first example of a structurally characterized ferrocenyl pnictogen where three 1,2-disubstituted ferrocenyl groups are attached to the central antimony atom and phosphorus analogue of the stibine is missing in the literature. Stibine (1) shows a hypervalent Sb–N interaction while stibine (2) does not show this interaction in solid state. 2008
First example of antimoniated Schiff bases: Hypervalent Sb? N (sp2) bonds https://www.sciencedirect.com/science/article/pii/S1387700306004527 The first example of antimoniated Schiff bases viz. 1-[2-(bis-{2-[(1-R-p-tolylethylimino)methyl]phenyl}stibanyl)benz-E-ilidene]-(1-R-p-tolylethyl)amine (1) and tris[(R)-2-benzyliden-2-yl-amino)butan-1-ol]stibine (2) containing imino groups at the ortho position of aryl ring have been synthesized and characterized. The compounds were obtained by the reaction of tris(o-formylphenyl)stibine with R-4-dimethyl benzyl amine or (R)-2-aminobutan-1-ol, respectively. These chiral antimony based Schiff bases were characterized by IR, mass, 1H, 13C, NMR spectroscopy. The X-ray crystal structures of these two Schiff bases show hypervalent interactions between antimony and sp2 nitrogen atoms. 2007
Modification of Rhodium Catalyst with Stibines for Hydroformylation of 1-Pentene https://onlinelibrary.wiley.com/doi/abs/10.1002/jccs.200700097 Homogeneous hydroformylation of 1-pentene under synthesis gas experimental conditions was studied using RhClCO(PPh3)2 complex with different triarylstibines. Three different stibine ligands SbR3 [where R = 2,4,6-mesityl (TMS), 2-furyl (TFS), 2-N,N-dimethylbenzylamine (TDMBAS)], have been tested. It is interesting to note that 2:1 addition of these stibine ligands to the RhClCO(PPh3)2 complex catalyst increases the aldehydes yields with an appreciable n:iso ratio. The catalytic activity of the system shows a TDMBAS > TMS > TFS pattern which indicates that not only basicity of the ligand alone is playing a role in the activity but the steric effect is also very important, and it is combination of these two factors that contributes to the resulting catalytical activity. The maximum yield of aldehydes obtained were 98.7% with n/iso = 1.4 when RhClCO(PPh3)2 + TFS system was used and 93.7% with n/iso = 2.43 when TDMBAS ligand was studied. 2007
Formation of (vinyl-ferrocenyl) stibines involving ß-elimination: Hypervalent Sb–N bonding https://www.sciencedirect.com/science/article/pii/S0022328X07003002 Unusual syntheses of vinyl substituted ferrocenylstibines viz. diphenyl(2-vinylferrocenyl) stibine (2) and iodo-(N,N-dimethylaminoethylferrocenyl)(2-vinylferrocenyl)stibine (4) involving ß-elimination, are reported. Stibines Ph2SbFc (1) or Fc2SbCl (3) containing dimethylaminoethyl-pendant arm on a ferrocenyl ring on reaction with MeI gives vinyl substituted ferrocenylstibines. All the new stibines were characterized by IR, mass, 1H, 13C, COSY, HETCOR NMR spectroscopy. The structures of all of these 1,2-disubstituted ferrocenylstibines were determined by X-ray diffraction analyses. The compounds 3 and 4 show hypervalent bonding between the antimony and nitrogen atoms giving 6 and 5 coordinated antimony, respectively. This is the first report on ferrocenylstibines containing a vinyl group in their framework. 2007
trans-Dichlorobis [(S)-(–)-1-(1-naphthyl) ethylamine] palladium (II) https://scripts.iucr.org/cgi-bin/paper?FL6203 The title complex, [PdCl2(C12H13N2)2], has two amine ligands coordinated in such a way that the naphthyl and methyl groups are located in the same hemisphere with respect to the [PdN2Cl2] coordination plane. This configuration allows for the formation of dimers in the solid state with a metal–metal separation of 3.2499 (4) Å 2006
Conformational change induced by hydration: trans-dichlorobis [(1R, 2R, 3R, 5S)-(–)-isopinocampheylamine] palladium (II) and trans-dichlorobis [(1S, 2S, 3S, 5R) https://scripts.iucr.org/cgi-bin/paper?GZ1007 The title compounds, trans-dichlorobis[(1R,2R,3R,5S)-(-)-2,6,6-trimethylbicyclo[3.1.1]heptan-3-amine]palladium(II), [PdCl2(C10H19N)2], and trans-dichlorobis[(1S,2S,3S,5R)-(+)-2,6,6-trimethylbicyclo[3.1.1]heptan-3-amine]palladium(II) hemihydrate, [PdCl2(C10H19N)2]·0.5H2O, present different arrangements of the amine ligands coordinated to PdII, viz. antiperiplanar in the former case and (-)anticlinal in the latter. The hemihydrate is an inclusion compound, with a Pd coordination complex and disordered water molecules residing on crystallographic twofold axes. The crystal structure for the hemihydrate includes a short Pd?Pd separation of 3.4133 (13) Å. 2005
Solvent-free synthesis of chiral N, N’-disubstituted thioureas by ‘just mixing’the reagents https://www.thieme-connect.com/products/ejournals/html/10.1055/s-2004-829167 The synthesis of new chiral thioureas 3a-f by using the ecofriendly solvent-free and microwave-assisted approaches is reported and, unexpectedly, in the former method by just mixing the starting materials the products are instantaneously obtained. The crystal structures for 3b, 3c and 3e are also reported. 2004
Synthesis, crystal structure, weak antiferromagnetic behavior and electronic studies of novel. https://www.sciencedirect.com/science/article/abs/pii/S0022286003004137 complex is obtained by direct synthesis using copper(0). 1 crystallizes in the monoclinic space group P21 with a=14.7355(12), b=8.9768(5), ß=111.916(5)°, and Z=4. The electronic spectrum of 1 shows a broad band with characteristic of a low symmetry and tetragonally distorted square pyramidal local Cu geometry. The far IR spectrum of 1 shows characteristic vibrations of Cu–Cl (260, 267 cm-1), Cu–N (436, 467 cm-1) and Cu–O (457 cm-1) bonds. The 1H NMR spectrum of 1 is typical of magnetic Cu(II) complexes with line broadening due to efficient nuclear relaxation from the metal center. ESR spectra of polycrystalline 1 at 77 K show an axial spectrum with linewidth of 58.6 G and at 300 K of 89.0 G, with areas in the ratio A77/A300=2.79, indicative of antiferromagnetic order. The linewidth is reduced by 34% on going from 300 to 77 K. Standard magnetization measurements at low temperatures show an Curie–Weiss behavior with suggesting a weak exchange coupling interaction. The crystalline structure of 1 shows that the lattice is arranged so that the space between molecules is smaller than 40 Å3, not enough to accommodate solvent molecules. However, the shortest Cu–Cu contact is 7.5912(8) Å. 2003
Chiral complexes by direct synthesis of a biomolecule and metal powders. Crystal structures of the dichloro [(-)-SPARTEINE-N, N’] M (II) COMPLEXES (M= Cu, Zn) https://www.tandfonline.com/doi/abs/10.1080/00958970108022644 Direct synthesis of chiral complexes dichloro[(-)-sparteine-N,N’]copper(II) 2 and dichloro[(-)-sparteine-N,N’]zinc(II) 3 derived from a biomolecule-namely the natural base (-)-sparteine- and elemental metals (Cu and Zn) in a CCl4/DMSO solvent system (DMSO = dimethylsulfoxide) is reported. The complexes were partly characterized by spectroscopic methods and their structures were fully confirmed by single-crystal x-ray analysis. A comparison between the new crystal structures of 2 and 3 and that of the free ligand (-)-sparteine displayed only slight differences on the ligand framework. 2001