Alejandro Cruz - Academia.edu (original) (raw)
Papers by Alejandro Cruz
Molecules, 2021
Nowadays, organic chemists are interested in the field of heterocyclic chemistry due to its use i... more Nowadays, organic chemists are interested in the field of heterocyclic chemistry due to its use in the synthesis of a great variety of biologically active compounds. Heterocyclic compounds are widely found in nature and are essential for life. Among these, some natural nitrogen containing heterocyclic compounds have been used as chemotherapeutic agents. Their attachment to sugar molecules either as thioglycosides or as nucleosides analogues plays an important role in vital biological processes as well as in synthetic organic chemistry. Molecules containing benzothiazole (BT) nuclei are of this interesting class of compounds because some of them have been found to have a wide variety of biological activities. In this sense, we selected this topic to review and to then summarize the procedures related to the condensation reactions of o-aminothiophenoles (ATPs) as well as their disulfides with carboxylic acids, esters, orthoesters, acyl chlorides, amides, and nitriles. The condensation...
Molecules, 2019
In this investigation, the reaction of 2-dithiomethylcarboimidatebenzothiazole with a series of s... more In this investigation, the reaction of 2-dithiomethylcarboimidatebenzothiazole with a series of six chiral amino-acids was studied. The reaction proceeds through the isolable sodium salt of SMe-isothiourea carboxylates as intermediates, whose reaction with methyl iodide in stirring DMF as solvent affords SMe-isothiourea methyl esters. The presence of water in the reaction leads to the corresponding urea carboxylates as isolable intermediates, whose methyl esters were obtained. Finally, the urea N-methyl amide derivatives were isolated when SMe-isothiourea or urea methyl esters were reacted with methylamine in the presence of water. The structures of synthesized compounds were established by 1H and 13C nuclear magnetic resonance and the structures of SMe-isothiourea methyl esters derived from (l)-glycine, (l)-alanine, (l)-phenylglycine, and (l)-leucine, by X-ray diffraction analysis. This methodology allows to functionalize 2-aminobenzothiazole with SMe-isothiourea, urea, and methyla...
![Research paper thumbnail of Thermal [4 + 2] Cycloadditions of 3-Acetyl-, 3-Carbamoyl-, and 3-Ethoxycarbonyl-Coumarins with 2,3-Dimethyl-1,3-butadiene under Solventless Conditions: A Structural Study](https://attachments.academia-assets.com/95447911/thumbnails/1.jpg)
](Molecules, 2010
The thermal [4+2] cycloadditions of 3-acetyl-, 3-carbamoyl, and 3-ethoxycarbonylcoumarins with 2,... more The thermal [4+2] cycloadditions of 3-acetyl-, 3-carbamoyl, and 3-ethoxycarbonylcoumarins with 2,3-dimethyl-1,3-butadiene under solvent free conditions are reported, as well as the epoxidation reactions of some adducts. Discussion is focused on the structural features of the Diels-Alder adducts and their epoxides, based upon NMR, X-ray, and mass spectral data, and supported by ab initio theoretical calculations.
Tetrahedron: Asymmetry, 1998
The stereochemistry of the chlorination reactions with SOCl 2 of free ephedrine and pseudoephedri... more The stereochemistry of the chlorination reactions with SOCl 2 of free ephedrine and pseudoephedrine and their hydrochlorides, oxamides and sulfonamides was analyzed. Chlorination of free and hydrochloride erythro isomers occurs with 100% inversion of configuration at C-1 (S N 2 mechanism). Chlorination of oxamides and sulfonamides of erythro isomers occurs with retention of the configuration at C-1, (S N i mechanism). Chlorination reactions in all threo isomers and derivatives hydrochlorides, oxamides or sulfonamides gave the same ratio of erythro (40%) and threo isomers (60%) (S N 1 mechanism). Treatment of the isomeric mixture of the chlorodeoxyephedrine and chlorodeoxypseudoephedrine hydrochloride in DMSO with HCl changes the isomeric ratio, increasing the erythro isomer content (65%). Using the erythro ethanolamines it is possible to arrive stereoselectively at the erythro chloroamines if the compound is previously tosylated or converted to the amide, or to the threo chloroamines if the compound is directly chlorinated with SOCl 2 .
![Research paper thumbnail of X-Ray Supramolecular Structure, NMR Spectroscopy and Synthesis of 3-Methyl-1-phenyl-1H-chromeno[4,3-c]pyrazol-4-ones Formed by the Unexpected Cyclization of 3-[1-(Phenyl-hydrazono)ethyl]-chromen-2-ones](https://attachments.academia-assets.com/95447910/thumbnails/1.jpg)
](Molecules, 2011
The molecular structures of nine 3-methyl-1-phenyl-1H-chromeno[4,3c]pyrazol-4-one isomers, obtain... more The molecular structures of nine 3-methyl-1-phenyl-1H-chromeno[4,3c]pyrazol-4-one isomers, obtained by the oxidative cyclization of the corresponding 1phenylhydrazono chromen-2-ones with copper acetate as catalyst, are reported. The molecular and supramolecular structures of the 8-chloro, 8-bromo-and 8-nitro isomers 2b-d, were established by X-ray diffraction. The halogenated isomers 2b and 2c are isomorphs, they crystallize as a triclinic system, space group P-1 with two molecules in the asymmetric unit. Compound 2d crystallizes as a monoclinic system, space group P2 1 /m with two molecules in the unit cell. The 1-phenyl ring [Cg(4)] is almost perpendicularly positioned to the chromene-pyrazole ring system. This conformation is in agreement with the anisotropic NMR shielding effect exerted by the phenyl ring over H-9 in solution. The supramolecular architecture is almost controlled by C-H•••A (A = O, π) and face to face π-stacking interactions. The observed π-stacking trend between chromene and pyrazole rings is given by the overlapping between the best donor and acceptor rings in each compound.
Molecules, 2012
Symmetric and non-symmetric 2-(N-H, N-methyl, N-ethylenyl and N-aryl)guanidinebenzothiazoles were... more Symmetric and non-symmetric 2-(N-H, N-methyl, N-ethylenyl and N-aryl)guanidinebenzothiazoles were synthesized from the reaction of ammonia, methylamine, pyrrolidine and aniline with dimethyl benzodthiazol-2-yl-carbonodithioimidate (5) as intermediate. The products were characterized by 1 H-, 13 C-NMR spectroscopy and three of them by X-ray diffraction analysis. HN-phenyl protons formed intramolecular hydrogen bonds that assist the stereochemistry of the second substituent, whereas the HN-alkyl protons were involved in intermolecular hydrogen bonding.
Arkivoc, 2007
S-Methylisothioureas, 2-N-H,-N-alkyl and-N-aryl are synthesized from the reaction of ammonia or t... more S-Methylisothioureas, 2-N-H,-N-alkyl and-N-aryl are synthesized from the reaction of ammonia or the corresponding aromatic amines with benzothiazole dithiomethylcarboimidate. The reaction with pyrrolidine and piperazine are reported. Compounds were characterized by 1 H and 13 C NMR spectroscopy and the X-ray molecular structure of S-methy-Nbenzothiazolelisothiourea derivative is reported.
Current Organic Synthesis, 2015
The synthesis of high optical purity chiral compounds is of current importance in organic and org... more The synthesis of high optical purity chiral compounds is of current importance in organic and organometallic areas of the chemistry with further boost. Chiral compounds are important because of wide use in many areas such as pharmacy and food industry, etc. Reagents, catalysts or chiral auxiliaries that can control the stereochemistry of the products are required for the synthesis of chiral compounds. Furthermore, the reagents used must be able to be recycled. In recent decades, Ephedra derivative compounds have been widely used as catalyst chiral ligands or chiral inductors in asymmetric synthesis. To our knowledge, no review about Ephedra derivative compounds as chiral auxiliaries used with organometallics in alkylation reactions to carbonyl compounds, has been published. In this paper, the use of N-substituted and N-disubstituted ephedra compounds as chiral auxiliary ligands in alkylation, alkenylation and alquinilation reactions of carbonyl and imine compounds is summarized.
Alkaloids - Alternatives in Synthesis, Modification and Application
Ephedra compounds are well known due to their biological activity. They have been widely used in ... more Ephedra compounds are well known due to their biological activity. They have been widely used in asymmetric synthesis during the last decades. Recently, we have prepared reviews about the synthesis of acyclic and heterocyclic ephedra derivative compounds reported in the literature. In this chapter, the synthetic methodology to access acyclic and heterocyclic compounds derived from ephedra alkaloids and its structural analysis are discussed, included those due to the substitution of the hydroxy group by chlorine, sulfur, selenium, or nitrogen atoms. Biological activity analysis of some synthesized compounds was done, and some of them have displayed biological activity.
In this paper a new architecture for development of Semantic Web Applications for decision taking... more In this paper a new architecture for development of Semantic Web Applications for decision taking using the paradigm of Web-Based Education (WBE) is presented. This architecture is based on the IEEE 1484 LTSA (Learning Technology System Architecture) specification, Multi-Agent System (MAS) and the software components named Intelligent Reusable Learning Components Object Oriented (IRLCOO). IRLCOO are a special type of Sharable Content Object (SCO) used like composition units under the Sharable Content Object Reusable Model (SCORM). SCORM is used to create reusable and interoperable learning content. The new architecture is oriented to offer interoperability at level application under the philosophy of Service-Oriented Architecture (SOA).
Molecules, 2021
Nowadays, organic chemists are interested in the field of heterocyclic chemistry due to its use i... more Nowadays, organic chemists are interested in the field of heterocyclic chemistry due to its use in the synthesis of a great variety of biologically active compounds. Heterocyclic compounds are widely found in nature and are essential for life. Among these, some natural nitrogen containing heterocyclic compounds have been used as chemotherapeutic agents. Their attachment to sugar molecules either as thioglycosides or as nucleosides analogues plays an important role in vital biological processes as well as in synthetic organic chemistry. Molecules containing benzothiazole (BT) nuclei are of this interesting class of compounds because some of them have been found to have a wide variety of biological activities. In this sense, we selected this topic to review and to then summarize the procedures related to the condensation reactions of o-aminothiophenoles (ATPs) as well as their disulfides with carboxylic acids, esters, orthoesters, acyl chlorides, amides, and nitriles. The condensation...
Molecules, 2019
In this investigation, the reaction of 2-dithiomethylcarboimidatebenzothiazole with a series of s... more In this investigation, the reaction of 2-dithiomethylcarboimidatebenzothiazole with a series of six chiral amino-acids was studied. The reaction proceeds through the isolable sodium salt of SMe-isothiourea carboxylates as intermediates, whose reaction with methyl iodide in stirring DMF as solvent affords SMe-isothiourea methyl esters. The presence of water in the reaction leads to the corresponding urea carboxylates as isolable intermediates, whose methyl esters were obtained. Finally, the urea N-methyl amide derivatives were isolated when SMe-isothiourea or urea methyl esters were reacted with methylamine in the presence of water. The structures of synthesized compounds were established by 1H and 13C nuclear magnetic resonance and the structures of SMe-isothiourea methyl esters derived from (l)-glycine, (l)-alanine, (l)-phenylglycine, and (l)-leucine, by X-ray diffraction analysis. This methodology allows to functionalize 2-aminobenzothiazole with SMe-isothiourea, urea, and methyla...
Molecules, 2010
The thermal [4+2] cycloadditions of 3-acetyl-, 3-carbamoyl, and 3-ethoxycarbonylcoumarins with 2,... more The thermal [4+2] cycloadditions of 3-acetyl-, 3-carbamoyl, and 3-ethoxycarbonylcoumarins with 2,3-dimethyl-1,3-butadiene under solvent free conditions are reported, as well as the epoxidation reactions of some adducts. Discussion is focused on the structural features of the Diels-Alder adducts and their epoxides, based upon NMR, X-ray, and mass spectral data, and supported by ab initio theoretical calculations.
Tetrahedron: Asymmetry, 1998
The stereochemistry of the chlorination reactions with SOCl 2 of free ephedrine and pseudoephedri... more The stereochemistry of the chlorination reactions with SOCl 2 of free ephedrine and pseudoephedrine and their hydrochlorides, oxamides and sulfonamides was analyzed. Chlorination of free and hydrochloride erythro isomers occurs with 100% inversion of configuration at C-1 (S N 2 mechanism). Chlorination of oxamides and sulfonamides of erythro isomers occurs with retention of the configuration at C-1, (S N i mechanism). Chlorination reactions in all threo isomers and derivatives hydrochlorides, oxamides or sulfonamides gave the same ratio of erythro (40%) and threo isomers (60%) (S N 1 mechanism). Treatment of the isomeric mixture of the chlorodeoxyephedrine and chlorodeoxypseudoephedrine hydrochloride in DMSO with HCl changes the isomeric ratio, increasing the erythro isomer content (65%). Using the erythro ethanolamines it is possible to arrive stereoselectively at the erythro chloroamines if the compound is previously tosylated or converted to the amide, or to the threo chloroamines if the compound is directly chlorinated with SOCl 2 .
Molecules, 2011
The molecular structures of nine 3-methyl-1-phenyl-1H-chromeno[4,3c]pyrazol-4-one isomers, obtain... more The molecular structures of nine 3-methyl-1-phenyl-1H-chromeno[4,3c]pyrazol-4-one isomers, obtained by the oxidative cyclization of the corresponding 1phenylhydrazono chromen-2-ones with copper acetate as catalyst, are reported. The molecular and supramolecular structures of the 8-chloro, 8-bromo-and 8-nitro isomers 2b-d, were established by X-ray diffraction. The halogenated isomers 2b and 2c are isomorphs, they crystallize as a triclinic system, space group P-1 with two molecules in the asymmetric unit. Compound 2d crystallizes as a monoclinic system, space group P2 1 /m with two molecules in the unit cell. The 1-phenyl ring [Cg(4)] is almost perpendicularly positioned to the chromene-pyrazole ring system. This conformation is in agreement with the anisotropic NMR shielding effect exerted by the phenyl ring over H-9 in solution. The supramolecular architecture is almost controlled by C-H•••A (A = O, π) and face to face π-stacking interactions. The observed π-stacking trend between chromene and pyrazole rings is given by the overlapping between the best donor and acceptor rings in each compound.
Molecules, 2012
Symmetric and non-symmetric 2-(N-H, N-methyl, N-ethylenyl and N-aryl)guanidinebenzothiazoles were... more Symmetric and non-symmetric 2-(N-H, N-methyl, N-ethylenyl and N-aryl)guanidinebenzothiazoles were synthesized from the reaction of ammonia, methylamine, pyrrolidine and aniline with dimethyl benzodthiazol-2-yl-carbonodithioimidate (5) as intermediate. The products were characterized by 1 H-, 13 C-NMR spectroscopy and three of them by X-ray diffraction analysis. HN-phenyl protons formed intramolecular hydrogen bonds that assist the stereochemistry of the second substituent, whereas the HN-alkyl protons were involved in intermolecular hydrogen bonding.
Arkivoc, 2007
S-Methylisothioureas, 2-N-H,-N-alkyl and-N-aryl are synthesized from the reaction of ammonia or t... more S-Methylisothioureas, 2-N-H,-N-alkyl and-N-aryl are synthesized from the reaction of ammonia or the corresponding aromatic amines with benzothiazole dithiomethylcarboimidate. The reaction with pyrrolidine and piperazine are reported. Compounds were characterized by 1 H and 13 C NMR spectroscopy and the X-ray molecular structure of S-methy-Nbenzothiazolelisothiourea derivative is reported.
Current Organic Synthesis, 2015
The synthesis of high optical purity chiral compounds is of current importance in organic and org... more The synthesis of high optical purity chiral compounds is of current importance in organic and organometallic areas of the chemistry with further boost. Chiral compounds are important because of wide use in many areas such as pharmacy and food industry, etc. Reagents, catalysts or chiral auxiliaries that can control the stereochemistry of the products are required for the synthesis of chiral compounds. Furthermore, the reagents used must be able to be recycled. In recent decades, Ephedra derivative compounds have been widely used as catalyst chiral ligands or chiral inductors in asymmetric synthesis. To our knowledge, no review about Ephedra derivative compounds as chiral auxiliaries used with organometallics in alkylation reactions to carbonyl compounds, has been published. In this paper, the use of N-substituted and N-disubstituted ephedra compounds as chiral auxiliary ligands in alkylation, alkenylation and alquinilation reactions of carbonyl and imine compounds is summarized.
Alkaloids - Alternatives in Synthesis, Modification and Application
Ephedra compounds are well known due to their biological activity. They have been widely used in ... more Ephedra compounds are well known due to their biological activity. They have been widely used in asymmetric synthesis during the last decades. Recently, we have prepared reviews about the synthesis of acyclic and heterocyclic ephedra derivative compounds reported in the literature. In this chapter, the synthetic methodology to access acyclic and heterocyclic compounds derived from ephedra alkaloids and its structural analysis are discussed, included those due to the substitution of the hydroxy group by chlorine, sulfur, selenium, or nitrogen atoms. Biological activity analysis of some synthesized compounds was done, and some of them have displayed biological activity.
In this paper a new architecture for development of Semantic Web Applications for decision taking... more In this paper a new architecture for development of Semantic Web Applications for decision taking using the paradigm of Web-Based Education (WBE) is presented. This architecture is based on the IEEE 1484 LTSA (Learning Technology System Architecture) specification, Multi-Agent System (MAS) and the software components named Intelligent Reusable Learning Components Object Oriented (IRLCOO). IRLCOO are a special type of Sharable Content Object (SCO) used like composition units under the Sharable Content Object Reusable Model (SCORM). SCORM is used to create reusable and interoperable learning content. The new architecture is oriented to offer interoperability at level application under the philosophy of Service-Oriented Architecture (SOA).