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Molecules, Volume 8, Issue 5 (May 2003) – 7 articles , Pages 401-458

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223 KiB  
Article
Synthesis and Catalytic Activity of Two New Cyclic Tetraaza Ligands
by María Hechavarría Fonseca, Thomas Hjelmgaard and Burkhard König
Molecules 2003, 8(5), 453-458; https://doi.org/10.3390/80500453 - 31 May 2003
Cited by 1 | Viewed by 9073
Abstract
Two new chiral cyclic tetraaza ligands were synthesized and characterized. Their catalytic activity was tested in the asymmetric addition of diethylzinc to benzaldehyde. The expected secondary alcohol was obtained in moderate yields, but with very low enantioselectivity. Full article
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285 KiB  
Article
Synthesis of New Pyrazole and Pyrimidine Steroidal Derivatives
by Daniel G. Rivera, Klaus Peseke, Isabel Jomarrón, Alina Montero, Reinaldo Molina and Francisco Coll
Molecules 2003, 8(5), 444-452; https://doi.org/10.3390/80500444 - 31 May 2003
Cited by 15 | Viewed by 10814
Abstract
The synthesis of steroidal heterocycles containing the pyrazole and pyrimidine ring fused to the 16,17-position of the steroid nucleus is reported. Androstenolone acetate (1) reacted with carbon disulfide, iodomethane and sodium hydride to furnish 3β-acetoxy-16-[bis(methylthio)methylene]-5-androst-5-en-17-one (2). The reactions of 2 with hydrazine hydrate [...] Read more.
The synthesis of steroidal heterocycles containing the pyrazole and pyrimidine ring fused to the 16,17-position of the steroid nucleus is reported. Androstenolone acetate (1) reacted with carbon disulfide, iodomethane and sodium hydride to furnish 3β-acetoxy-16-[bis(methylthio)methylene]-5-androst-5-en-17-one (2). The reactions of 2 with hydrazine hydrate and methylhydrazine afforded the 5’-methylthio- pyrazolo[4’,3’:16,17]androst-5-en-3β-ols 3a and 3b, respectively. Treatment of 2 with amidinium, guanidinium, and isothiuronium salts in the presence of sodium methoxide yielded the 6’-methoxy-pyrimido[5’,4’:16,17]androst-5-en-3β-ols (4a-4e). Full article
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231 KiB  
Article
Synthesis of Some Transition Metal Complexes of a Novel Schiff Base Ligand Derived from 2,2'-bis(p-Methoxyphenylamine) and Salicylicaldehyde
by Xishi Tai, Xianhong Yin, Qiang Chen and Minyu Tan
Molecules 2003, 8(5), 439-443; https://doi.org/10.3390/80500439 - 31 May 2003
Cited by 66 | Viewed by 11864
Abstract
A novel Schiff base ligand derived from 2,2'-bis(p-methoxyphenylamine) and salicylicaldehyde and its transition metal complexes with Cu (Ⅱ), Co (Ⅱ) and Mn (Ⅱ) have been synthesized. Their spectral properties and electrochemical behavior were investigated. Full article
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250 KiB  
Article
Structures and Chemical Equilibria of Some N-Heterocycles Containing Amide Linkages
by M. S. Masoud, M. Abd El Zaher Mostafa, R. H. Ahmed and N. H. Abd El Moneim
Molecules 2003, 8(5), 430-438; https://doi.org/10.3390/80500430 - 31 May 2003
Cited by 15 | Viewed by 9639
Abstract
Structures and chemical equilibria of 5-carboxy-2-thiouracil (1), 5,6-diphenyl-3-hydroxy-1,2,4-triazine (2), 1-phenyl-3-methyl-5-pyrazolone (3) and 2-mercapto-4,6-dimethylpyrimidine hydrochloride (4) are reported. Their electronic transitions are assigned and pK values are evaluated and discussed. Full article
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427 KiB  
Article
Theoretical Study on the Interaction of o-Tetrafluorophenylene Mercury with Ethylene and Acetylene
by Eduardo A. Castro
Molecules 2003, 8(5), 418-429; https://doi.org/10.3390/80500418 - 31 May 2003
Cited by 1 | Viewed by 10201
Abstract
The results of a theoretical study on the interaction of o-tetrafluorophenylene mercury with ethylene and acetylene are reported. The AM1 molecular orbital semiempirical method is applied through a complete optimization procedure without any restrictions to find the optimal equilibrium geometries. The comparative capabilities [...] Read more.
The results of a theoretical study on the interaction of o-tetrafluorophenylene mercury with ethylene and acetylene are reported. The AM1 molecular orbital semiempirical method is applied through a complete optimization procedure without any restrictions to find the optimal equilibrium geometries. The comparative capabilities of ethylene and acetylene molecules to form stable complexes with o-tetrafluorophenylene mercury are analyzed and their corresponding bonding features are discussed. Ethylene seems to be capable of forming a molecular complex while acetylene is predicted to be incapable of doing so. Full article
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333 KiB  
Article
Synthesis and Structure of bis(Dibutyldithiocarbamate)zinc(II): Zn2[(n-Bu)2NCSS]4
by Weiguang Zhang, Yun Zhong, Minyu Tan, Ning Tang and Kaibei Yu
Molecules 2003, 8(5), 411-417; https://doi.org/10.3390/80500411 - 31 May 2003
Cited by 17 | Viewed by 11934
Abstract
The binuclear zinc (II) complex Zn2[(n-Bu)2NCSS]4 has been prepared, and its crystal and molecular structure have been determined by x-ray diffraction. The crystal is monoclinic, space group C2/c, with a=23.329(3)Å, b=17.090(2)Å, c=16.115(2)Å, α =90°, β=127.560(10)°, γ=90°, z=4, V=5039.1(11)Å3, F(000)=2016, R=0.0450, and [...] Read more.
The binuclear zinc (II) complex Zn2[(n-Bu)2NCSS]4 has been prepared, and its crystal and molecular structure have been determined by x-ray diffraction. The crystal is monoclinic, space group C2/c, with a=23.329(3)Å, b=17.090(2)Å, c=16.115(2)Å, α =90°, β=127.560(10)°, γ=90°, z=4, V=5039.1(11)Å3, F(000)=2016, R=0.0450, and Rw=0.1192. The crystal structure shows that two S-N-S atom chains, belonging to the different dibutyldithiocarbamate ligands, bridge two zinc (II) ions. Each zinc (II) ion coordinates to four S atoms. The coordination geometry around the zinc (II) is a tetrahedron, however, the coordination sphere of two zinc ions in the dimer is best described as a distorted octagon. The X-ray photoelectron spectra, IR and UV data have been used to study the structure and spectra properties of the complex. Full article
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291 KiB  
Article
Dipolar Cycloaddition Reactions with Quinazolinones: A New Route for the Synthesis of Several Annelated Pyrrolo- and Pyridazinoquinazoline Derivatives
by Sami S. Ghabrial and Hatem M. Gaber
Molecules 2003, 8(5), 401-410; https://doi.org/10.3390/80500401 - 31 May 2003
Cited by 18 | Viewed by 8645
Abstract
The novel 2-aryl-3a,4,12,12a-tetrahydropyrrolo[3',4':4,3]-pyridazino[6,1-b]-quinazoline-1,3,6-triones (6a–d), 2-aryl-10-oxopyridazino[6,1-b]-quinazoline-3-thio-carboxamides (10a–d) and 2-aryl-3-nitro-1,2,3,4-tetrahydro-pyridazino[6,1-b]quinazolin-10-ones (12a–d) were synthesized via a new, facile one step route involving the reactions of the zwitterion 4, formed in situ, with a variety of N-arylmaleimides 5, 3-aryl-2-cyano-thioacrylamides 8 and ω-nitrostyrenes 11. Dehydrogenation of [...] Read more.
The novel 2-aryl-3a,4,12,12a-tetrahydropyrrolo[3',4':4,3]-pyridazino[6,1-b]-quinazoline-1,3,6-triones (6a–d), 2-aryl-10-oxopyridazino[6,1-b]-quinazoline-3-thio-carboxamides (10a–d) and 2-aryl-3-nitro-1,2,3,4-tetrahydro-pyridazino[6,1-b]quinazolin-10-ones (12a–d) were synthesized via a new, facile one step route involving the reactions of the zwitterion 4, formed in situ, with a variety of N-arylmaleimides 5, 3-aryl-2-cyano-thioacrylamides 8 and ω-nitrostyrenes 11. Dehydrogenation of the tetrahydro derivatives 6a–d and 12a–d in nitrobenzene resulted in the formation of 2-arylpyrrolo[3',4':4,3]-pyridazino[6,1-b]quinazoline-1,3,6-triones (7a–d) and 2-aryl-3-nitropyridazino[6,1-b]quinazolin-10-ones (13a–d), respectively. The structures of the products were confirmed by elemental analysis and spectral data. Full article
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