Molecules

77 KiB

Open AccessArticle

Synthesis of 1-Benzyl-6-(4-chlorophenyl)-2-(4-R-phenyl)-4-(4-Rstyryl)-2,3-dihydropyrazolo[3,4-b][1,4]diazepines

by Braulio Insuasty, Ricaurte Rodríguez, Jairo Quiroga, Rodrigo Abonía, Roberto Martínez, Alfredo Toscano and E. Angeles

Molecules 2001, 6(8), 710-715; https://doi.org/10.3390/60800710 - 31 Jul 2001

Cited by 12 | Viewed by 7987

Abstract

The reaction of 4-amino-5-benzylamino-3-(4-chlorophenyl)-1H-pyrazole (1) with substituted diarylidenketones (2) constitutes a convenient synthetic route to the hitherto unknown 1-benzyl-6-(4-chlorophenyl)-2-(4-R-phenyl)-4-(4-R-styryl)-2,3-dihydropyrazolo-[3,4-b][1,4]diazepines (3). Structures of all products were consistent with their IR, ¹H-NMR, ¹³C-NMR and MS spectral data. X-ray crystallography data confirm the assigned structures. Full article

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62 KiB

Open AccessArticle

Solvent and Substituent Effects on the Kinetics of Thermolysis of cis-Fused 1,2,4-Trioxanes

by Lázaro F. R. Cafferata and Charles W. Jefford

Molecules 2001, 6(8), 699-709; https://doi.org/10.3390/60800699 - 31 Jul 2001

Cited by 8 | Viewed by 11430

Abstract

The kinetics of the thermal decomposition reaction of cis-6-phenyl-5,6-(2-phenylpropyliden)-3,3-pentamethylene-1,2,4-trioxacyclohexane (Ia) were investigated in benzene and methanol solutions in the temperature and concentration ranges of 353.3 – 413.2 K and (1.1 – 13.1)x10^-3 M, respectively. First-order rate constant values were obtained for up [...] Read more.

The kinetics of the thermal decomposition reaction of cis-6-phenyl-5,6-(2-phenylpropyliden)-3,3-pentamethylene-1,2,4-trioxacyclohexane (Ia) were investigated in benzene and methanol solutions in the temperature and concentration ranges of 353.3 – 413.2 K and (1.1 – 13.1)x10^-3 M, respectively. First-order rate constant values were obtained for up to at least ca. 20% conversions of that cyclic peroxide. The activation parameter values for the initial unimolecular homolysis of that molecule, results supported by the effect of the addition of di-tert-butyl-p-cresol as a free radical scavenger, indicate a stepwise reaction mechanism which is in keeping with the reaction products analysis. The corresponding activation parameters for the reaction of Ia in methanol (ΔH# = 20.2 ± 0.6 kcal mol^-1; ΔS^# = 0.1 ± 1.6 cal mol^-1 K-1; ΔG^# = 20.2 ± 0.6 kcal mol^-1) and in benzene (ΔH^# = 15.4 ± 0.2 kcal mol^-1; ΔS^# = -13.2 ± 0.5 cal mol^-1 K^-1; ΔG^# = 20.5 ± 0.2 kcal mol^-1) solutions are compared with values obtained for cis-6-phenyl-5,6-(2-phenylpropyliden)-3,3-tetramethylene-1,2,4-trioxacyclohexane (Ib) thermolysis in the same solvents. The thermolysis kinetics of Ia are less sensitive to solvent changes compared to the behaviour already reported for the analogous reactions of Ib. Because both molecules in solution are flexible structures due to their configurations, the relatively small solvent effect found on the former trioxane reaction is attributed to the extent of the chain of methylene groups attached on C-3 of the corresponding molecular rings. Furthermore, the pertinent substituent effect on the peroxidic bond strength of those molecules in solution was evaluated. Full article

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26 KiB

Open AccessArticle

An Efficient and Chemoselective Method for Oximination of β-Diketones Under Mild and Heterogeneous Conditions

by Mohammad Ali Zolfigol

Molecules 2001, 6(8), 694-698; https://doi.org/10.3390/60800694 - 31 Jul 2001

Cited by 14 | Viewed by 8922

Abstract

A combination of oxalic acid dihydrate and sodium nitrite in the presence of wet SiO₂ was used as an effective nitrosating agent for the nitrosation of β-diketones to their corresponding α-oximinoketones in moderate to excellent yields under mild and heterogenous conditions. Full article

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51 KiB

Open AccessArticle

Synthesis of new Bis- and Tetra-Acridines

by Valérie Sourdon, Stéphane Mazoyer, Valérie Pique and Jean-Pierre Galy

Molecules 2001, 6(8), 673-682; https://doi.org/10.3390/60800673 - 31 Jul 2001

Cited by 34 | Viewed by 8416

Abstract

A new series of bis- and tetra-acridines has been prepared from 4-(bromomethyl) acridine; some of them exhibited encouraging in vitro cytotoxic activities against murine cell lines. Full article

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23 KiB

Open AccessArticle

Modified Methods for the Synthesis of Carbazole from Phenothiazine

by R. Bryan Miller and Steven C. Farmer

Molecules 2001, 6(8), 668-672; https://doi.org/10.3390/60800668 - 31 Jul 2001

Cited by 6 | Viewed by 6628

Abstract

Lithium, used in conjunction with triphenylphosphine or sodium metal, produces a high yield of carbazole when reacted with phenothiazine. Full article

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27 KiB

Open AccessArticle

Stilbenes and a New Acetophenone Derivative from Scirpus holoschoenus

by M. Abdel-Mogib, S. A. Basaif and T. R. Sobahi

Molecules 2001, 6(8), 663-667; https://doi.org/10.3390/60800663 - 31 Jul 2001

Cited by 16 | Viewed by 7619

Abstract

Separation of the extract of the tubers of Scirpus holoschoenus L. (family Cyperaceae), a species easily confused with Juncus plants, afforded 2-prenyl-3,5,4'-trimethoxystilbene, 2-prenyl-3-hydroxy-5,4'-dimethoxystilbene, 2-prenyl-3,4'-dihydroxy-5-methoxy-stilbene and 3,5,4'-trimethoxystilbene, in addition to a new acetophenone derivative. The isolated compounds were identified on the basis of spectral [...] Read more.

Separation of the extract of the tubers of Scirpus holoschoenus L. (family Cyperaceae), a species easily confused with Juncus plants, afforded 2-prenyl-3,5,4'-trimethoxystilbene, 2-prenyl-3-hydroxy-5,4'-dimethoxystilbene, 2-prenyl-3,4'-dihydroxy-5-methoxy-stilbene and 3,5,4'-trimethoxystilbene, in addition to a new acetophenone derivative. The isolated compounds were identified on the basis of spectral measurements. Full article

35 KiB

Open AccessArticle

Use of Cyclic Allylic Bromides in the Zinc–Mediated Aqueous Barbier–Grignard Reaction

by Gary W. Breton, John H. Shugart, Christine A. Hughey, Brian P. Conrad and Suzanne M. Perala

Molecules 2001, 6(8), 655-662; https://doi.org/10.3390/60800655 - 31 Jul 2001

Cited by 19 | Viewed by 12071

Abstract

The zinc–mediated aqueous Barbier–Grignard reaction of cyclic allylic bromide substrates with various aldehydes and ketones to afford homoallylic alcohols was investigated. Aromatic aldehydes and ketones afforded adducts in good yields (66–90%) and with good diastereoselectivities. Non–aromatic aldehydes also reacted well under these conditions, [...] Read more.

The zinc–mediated aqueous Barbier–Grignard reaction of cyclic allylic bromide substrates with various aldehydes and ketones to afford homoallylic alcohols was investigated. Aromatic aldehydes and ketones afforded adducts in good yields (66–90%) and with good diastereoselectivities. Non–aromatic aldehydes also reacted well under these conditions, but only poor yields were obtained with non–aromatic ketones. Regioselectivity was high when some substituted cyclic allylic bromides were investigated. Full article

101 KiB

Open AccessArticle

Synthesis, Structure and Antitumor Activity of Dibutyltin Oxide Complexes with 5-Fluorouracil Derivatives. Crystal Structure of [(5-Fluorouracil)-1-CH₂CH₂COOSn(n-Bu) ₂]₄O₂

by Dai-shu Zuo, Tao Jiang, Hua-shi Guan, Kui-qi Wang, Xin Qi and Zhan Shi

Molecules 2001, 6(8), 647-654; https://doi.org/10.3390/60800647 - 31 Jul 2001

Cited by 14 | Viewed by 10335 | Retraction

Abstract

Dibutyltin (IV) oxide complex reacts with the fluorouracil compounds 5-fluorouracil-1-propanonic or 5-fluorouracil-1-acetic acid (Fu) to give the complexes [(5-Fu)-1-(CH₂)_nCOOSn(n-Bu)₂]₄O₂ (I, n=2; II, n=1) which were characterized by IR and ¹H-NMR. The [...] Read more.

Dibutyltin (IV) oxide complex reacts with the fluorouracil compounds 5-fluorouracil-1-propanonic or 5-fluorouracil-1-acetic acid (Fu) to give the complexes [(5-Fu)-1-(CH₂)_nCOOSn(n-Bu)₂]₄O₂ (I, n=2; II, n=1) which were characterized by IR and ¹H-NMR. The crystal structure of complex I shows that the molecular is a dimer, in which two [(5-Fu)-1-CH₂CH₂COOSn(n-Bu)₂]₂O units are linked by a bridging oxygen atom, and the tin atoms adopt distorted trigonal bipyramids via two carbons from a dibutyl moiety and three oxygen atoms from 5-Fu and bridging oxygen. These complexes have potential anti-tumour activity: in vitro tests showed that complexes I and II exhibit high cytotoxicity against OVCAR-3 and PC-14. Full article

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68 KiB

Open AccessArticle

Rearrangement of o-Nitrobenzaldehyde in the Hantzsch Reaction

by E. Angeles, H. Santillán, I. Menconi, I. Martínez, A. Ramírez, A. Velázquez, R. López- Castañares and R. Martínez

Molecules 2001, 6(8), 683-693; https://doi.org/10.3390/60800683 - 21 Jul 2001

Cited by 7 | Viewed by 11528

Abstract

The reaction of 5-hydroxy-2-nitrobenzaldehyde with ethyl acetoacetate in ammonia gave the two expected isomeric 1,4- and 1,2-dihydropyridines resulting from the normal Hantzsch reaction. However, the combination of 2-nitrobenzaldehyde with ethyl acetoacetate under the same conditions yielded four products: the two normal isomeric dihydropyridines [...] Read more.

The reaction of 5-hydroxy-2-nitrobenzaldehyde with ethyl acetoacetate in ammonia gave the two expected isomeric 1,4- and 1,2-dihydropyridines resulting from the normal Hantzsch reaction. However, the combination of 2-nitrobenzaldehyde with ethyl acetoacetate under the same conditions yielded four products: the two normal isomeric dihydropyridines and two tricyclic compounds. When we attempted to independently synthesize the two tricyclic compounds by reductive cyclization of 4-(2-nitrophenyl)-2,6-dimethyl-3,5-dicarbetoxy-1,4-dihydropyridine and 2-(2-nitrophenyl)-4,6-dimethyl-3,5-dicarbetoxy-1,2-dihydropyridine with tin (II) chloride in hydrochloric acid media, we obtained instead an indole and a quinoline derivative, respectively. Full article

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Molecules, Volume 6, Issue 8 (August 2001) – 9 articles , Pages 647-715

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