Stereocontrolled catalytic hydrogenations of 3-oxocholestanes and some related compounds to the corresponding axial 3-alcohols

1980 ◽  
Vol 58 (11) ◽  
pp. 1061-1068 ◽  
Author(s):  
Masayoshi Ishige ◽  
Michio Shiota
Keyword(s):  
Carbonyl Group ◽  
Cobalt Catalyst ◽  
Solvent Polarity ◽  
The Other ◽  
Nonpolar Solvents ◽  
Ketone Carbonyl Group ◽  
Other Hand ◽  
Ketone Carbonyl ◽  
Related Compounds ◽  
Alcohol Formation

Catalytic hydrogenations of 5α-cholestan-3-ones and related compounds with Urushibara nickel A catalyst in cyclohexane gave a distinct preponderance of unstable axial 3α-ols. Product ratios of axial alcohols decreased with increasing solvent polarity. For 3-oxo-5α-steroids, the cobalt catalyst was less selective for the axial alcohol formation. On the other hand, conversion of 5β-cholestan-3-one into the corresponding axial 3β-ol was most successfully attained by hydrogenation catalyzed by Urushibara cobalt A catalyst in methanol. For such a 5β-ketone, alcoholic media with higher polarities were more favorable for giving the product rich in axial alcohol. The stereochemistry of the products obtained from hydrogenations conducted in nonpolar solvents may be understood in terms of the steric congestion around the ketone carbonyl group. However, when alcohols were used as solvents, the product ratios obtained did not correlate well with the congestion ratios of substrates.

Alkylation by secondary alcohols. I. The reaction of xanthydrol with some N1-monosubstituted sulfanilamides and related compounds

1967 ◽  
Vol 45 (13) ◽  
pp. 1411-1424 ◽  
Author(s):  
R. E. Moskalyk ◽  
L. G. Chatten
Keyword(s):  
Nitrogen Atom ◽  
Tautomeric Form ◽  
Heterocyclic Ring ◽  
The Other ◽  
Secondary Alcohols ◽  
Amino Group ◽  
Aromatic Character ◽  
Carbonium Ion ◽  
Other Hand ◽  
Related Compounds

Sulfanilamides were found to undergo alkylation with xanthydrol, yielding either mono- or di-xanthenyl derivatives. The site of substitution, common to all sulfanilamides having a free p-amino group, was shown to be the N4-position in the sulfanilamide molecule. Three additional unique reactive sites were observed. Sulfanilamides carrying a thiazole, thiadiazole, or pyridazine substituent in the N1-position were also alkylated on the annular nitrogen atom of the heterocyclic ring, the reaction having occurred from the imido tautomeric form. Sulfisoxazole (IK), on the other hand, reacted from the amido form to give the N1,N4-dixanthenyl derivative. Sulfadimethoxine (Ih) was substituted at carbon, as well as at nitrogen, to yield N4-xanthenyl-N1-(2,6-dimethoxy-5-(9-xanthenyl)-4-pyrimidyl)sulfanilamide.Sulfanilamides possessing pKa values of about 5.5 were found to be sufficiently acidic to catalyze their own reaction with xanthydrol, and no external catalyst was necessary. The exceptional ease of formation of the xanthylium ion was postulated to be associated with the resulting stability of this carbonium ion by virtue of its acquired aromatic character.

Complexes moléculaires d'hétérocycles soufrés et oxygénés. Étude spectrophotométrique de bandes de transfert de charge multiples

1982 ◽  
Vol 60 (7) ◽  
pp. 862-871 ◽  
Author(s):  
Jean-Paul Canselier ◽  
Serge Domenech ◽  
Štefan Stankovsky ◽  
Sabine Gautier
Keyword(s):  
Charge Transfer ◽  
Absorption Spectra ◽  
Electronic Absorption ◽  
Electronic Absorption Spectra ◽  
Molecular Complexes ◽  
The Other ◽  
Ionization Potentials ◽  
Nonpolar Solvents ◽  
Other Hand ◽  
The One

As with benzenoid donors, the electronic absorption spectra of the molecular complexes of simple or condensed sulfur or oxygen-containing five-membered heterocycles with TCNE (or DDQ) often show two charge-transfer bands. In many cases, the knowledge of the actual frequencies requires a technique of resolution. The results so obtained are correlated with the ionization potentials of donors on the one hand, and the refractivity of nonpolar solvents on the other hand.

Synthesis of Some Diazepinones, Oxazepinones, Pyrimidoquinazolinones and Related Compounds from 1,4-Bis(ethoxycarbonyl)-2,5-diamino-1,4-cyclohexadiene

1980 ◽  
Vol 35 (11) ◽  
pp. 1395-1397 ◽  
Author(s):  
Fathy A. Amer ◽  
El-Sayed Afsah ◽  
Mohamed A. Metwally ◽  
Mohamed T. El-Zimaity
Keyword(s):  
Polyphosphoric Acid ◽  
The Other ◽  
Spectroscopic Methods ◽  
Other Hand ◽  
Related Compounds

AbstractInteraction of o-phenylenediamine with 1,4-Bis-(ethoxycarbonyl)-2,5-diamino-1,4-cyclo-hexadiene (1) gave 2, which cyclised to the hexahydrobenzodiazepinone (3). On the other hand, interaction of 1 with o-aminophenol, gave compound 4 which on treatment with polyphosphoric acid gave the tetrahydrobis-benzooxazepinone (11). Treatment of 1 with phenylisothiocyanate and formamide afforded the dithiopyrimidoquinazolinone (8) and the tetrahydropyrimidoquinazolinone (9), while the interaction of 1 with benzenesulphonyl-chloride gave dibenzenesulphonamido-cyclohexadiene dicarboxylate (10). The structure of these compounds was established by chemical and spectroscopic methods.

Pyrimidine Derivatives and Related Compounds, IX / Preparation of 5-Aminopyrazolo[1,5-a]pyrimidines and of Oxazino[4,5 : 5,6]pyrazolo[1,5-a]pyrimidines, a New Ring System

1977 ◽  
Vol 32 (12) ◽  
pp. 1478-1481 ◽  
Author(s):  
Mohamed Hilmy Elnagdi ◽  
Sherif Mahmoud Fahmy ◽  
Mohamed Riffaat Hamza Elmoghayar ◽  
Abdalla Mohamed Negm
Keyword(s):  
Acetic Acid ◽  
Pyrimidine Derivative ◽  
Ring System ◽  
The Other ◽  
Reaction Products ◽  
Pyrimidine Derivatives ◽  
Other Hand ◽  
Related Compounds

Whereas the 5-aminopyrazole derivatives (1 a, b) react with ethyl β-amino-β-trichloro-methylmethylenecyanoacetate (2) in basic media to yield the corresponding 5-aminopyrazolo[1,5-a]pyrimidine derivatives (3a, b), the reaction of la, b with 2 in refluxing acetic acid has afforded oxazino[4,5:5,6]pyrazolo[1,5-a]pyrimidine derivatives.5-Amino-3-phenyl-4-phenylazopyrazole (12) reacted with 2 in refluxing pyridine to yield the 5-amino-2-phenyl-3-phenylazopyrazolo[1,5-a]pyrimidine derivative (18). On the other hand, the reaction of 12 and 2 in refluxing acetic acid has afforded a mixture of the oxazino[4,5:5′,6′]pyrazolo[1,5-a]pyrimidine derivatives (14) and the pyrazolo[3,4-d]-astriazine derivatives (15). The mechanism of the formation of reaction products is discussed.

Synthesis of 2-Acetoacetyl- and 2-OxaIoacetyl-1,3-indandiones and Related Compounds

1988 ◽  
Vol 43 (7) ◽  
pp. 897-900 ◽  
Author(s):  
W. S. Hamama ◽  
M. Hammouda ◽  
E. M. Afsah
Keyword(s):  
Ethyl Acetate ◽  
Mannich Reaction ◽  
Selenium Dioxide ◽  
The Other ◽  
Molar Ratio ◽  
Diethyl Oxalate ◽  
Phenyl Hydrazine ◽  
Claisen Condensation ◽  
Other Hand ◽  
Related Compounds

Abstract Claisen condensation of 2-acetyl-1,3-indandione (1) with ethyl acetate afforded the 2-acetoacetyl-1,3-indandione (2) which upon treatment with benzylamine and paraformaldehyde in a molar ratio of (1:1:2) and (1:2:4) afforded the piperidinone and the diazabicyclic derivative (4) and (5) respectively. On the other hand, Claisen condensation of 1 with diethyl oxalate yielded two products (6) and (9). The behaviour of 6 towards phenyl hydrazine, and of 9 towards selenium dioxide and double Mannich reaction were also investigated.

Pyrimidine Derivatives and Related Compounds, III / Synthesis of Some New Pyrazolo [1,5-a] pyrimidines and Pyrazolo [3,4-d] pyrimidine Derivatives

1976 ◽  
Vol 31 (6) ◽  
pp. 795-800 ◽  
Author(s):  
Mohamed Hilmy Elnagdi ◽  
Sherief Mahmoud Fahmy ◽  
Ezzat Mohamed Zayed ◽  
Mohamed Ajmal Mohamed Ilias
Keyword(s):  
Acetic Acid ◽  
Carbon Disulphide ◽  
Pyrimidine Derivative ◽  
The Other ◽  
Acid Mixture ◽  
Pyrimidine Derivatives ◽  
Other Hand ◽  
Naoh Solution ◽  
Related Compounds ◽  
Hydrazone Derivative

Whereas β-cyanoethylhydrazine (1) reacts with the β-ethoxy-α,β-unsaturated nitriles (2a—c) to yield the 5-amino-1-B-cyanoethylpyrazoles (8a—c), 1 reacts with anilinomethylenemalononitrile (2d) to yield 3-amino-1-B-cyanoethyl-4-cyanopyrazole (4; R=H; X=CN). 3a readily cyclised into the 5-amino-6,7-dihydropyrazolo[1,5-a]pyrimidine derivative (6) by the action of ethanolic guanidine. 6 was readily converted into the oxo derivative (7) by the action of acetic acid. 7 was also obtained by the action of 1% NaOH on 3a. On the other hand, 3b afforded a mixture of the pyrazolo[1,5-a]pyrimidine derivative (8) and the carboxylic acid (9) when treated with 1% NaOH solution.3-Aminocrotononitrile (2e) reacted with 1 to yield the hydrazone derivative (12). The latter derivative was converted into the pyrazolo[1,5-a]pyrimidine derivative (14) by the action of acetic acid. On the other hand, the hydrochloride (15) was formed on treatment of 12 with acetic acid hydrochloric acid mixture.Compounds 8 a, b reacted with carbon disulphide to yield the pyrazolo[3,4-d]-6 (7 H)-m- thiazinethione derivatives (16a,b). The latter were readily converted into the pyrazolo-[3,4-d]pyrimidine derivatives (17 a, b) by the action of aqueous NaOH solution.

Article

1998 ◽  
Vol 76 (4) ◽  
pp. 490-497
Author(s):  
Okba Saied ◽  
Benoit Bachand ◽  
James D Wuest
Keyword(s):  
Carbonyl Group ◽  
Carbonyl Compounds ◽  
Lewis Acids ◽  
Carbonyl Oxygen ◽  
The Other ◽  
Keto Group ◽  
Carbonyl Groups ◽  
Lone Pairs ◽  
Related Compounds ◽  
Oxygen Atoms

Carbonyl oxygen atoms have two formal lone pairs of electrons. In principle, both can be used simultaneously to form complexes with two or more Lewis acids. This multiple coordination promises to have a variety of interesting consequences; unfortunately, however, complexes of carbonyl compounds with multiple Lewis acids are extremely rare. To promote multiple coordination, we have made a series of symmetric ketodiesters and related compounds in which the carbonyl group of a ketone is flanked by two additional sites of Lewis basicity. In such compounds, the flanking bases and both lone pairs of the central ketone are available for binding two equivalents of suitable Lewis acids, thereby producing symmetric double chelates in which the central ketone interacts with two Lewis acids at the same time. As expected, treatment of 3-oxoglutarates and 4-oxopimelates with TiCl4 in a 1:1 ratio yielded unsymmetric single chelates in which the carbonyl groups of the ketone and one ester bind TiCl4, while the other ester remains free. Unfortunately, treatment of the same ketodiesters with TiCl4 in a 1:2 ratio did not produce the desired symmetric double chelates. Instead, 2:4 complexes were formed in which the free esters of the unsymmetric single chelates bind TiCl4 in the normal way, without assistance from the keto group. We attribute this observation to the inherent reluctance of ketones to bind multiple Lewis acids, as well as to unfavorable Cl · · ·Cl interactions created in the hypothetical double chelates by the simultaneous attachment of two octahedrally coordinated atoms of titanium to a single carbonyl oxygen atom.Key words: Lewis acids, chelation, ketodiesters, TiCl4.

Investigation of the Thionation Reaction of Cyclic Imides

2001 ◽  
Vol 56 (10) ◽  
pp. 1035-1040 ◽  
Author(s):  
A. Orzeszko ◽  
J. K. Maurin ◽  
D. Melon-Ksyta
Keyword(s):  
Oxygen Atom ◽  
Carbonyl Group ◽  
Steric Hindrance ◽  
The Other ◽  
Carbonyl Groups ◽  
Other Hand ◽  
Cyclic Imides ◽  
Lawesson's Reagent ◽  
Main Effects ◽  
High Polarity

A series of monothioimides and dithioimides were synthesised using Lawesson’s reagent. It has been found that two main effects affect thionation reaction. The high polarity of carbonyl groups leads to good yields of mono- and dithioimides. On the other hand, steric hindrance in the vicinity of the carbonyl group strongly inhibits the replacement of the oxygen atom by sulfur.

A study of cometary eruptions through OH radio-lines

1999 ◽  
Vol 173 ◽  
pp. 249-254
Author(s):  
A.M. Silva ◽  
R.D. Miró
Keyword(s):  
Short Duration ◽  
Growth Curves ◽  
The Other ◽  
Initial Mass ◽  
Radio Lines ◽  
Other Hand ◽  
Sudden Rise

AbstractWe have developed a model for theH2OandOHevolution in a comet outburst, assuming that together with the gas, a distribution of icy grains is ejected. With an initial mass of icy grains of 108kg released, theH2OandOHproductions are increased up to a factor two, and the growth curves change drastically in the first two days. The model is applied to eruptions detected in theOHradio monitorings and fits well with the slow variations in the flux. On the other hand, several events of short duration appear, consisting of a sudden rise ofOHflux, followed by a sudden decay on the second day. These apparent short bursts are frequently found as precursors of a more durable eruption. We suggest that both of them are part of a unique eruption, and that the sudden decay is due to collisions that de-excite theOHmaser, when it reaches the Cometopause region located at 1.35 × 105kmfrom the nucleus.

Closing the GAP—A 5Å Scanning Microscope

1969 ◽  
Vol 27 ◽  
pp. 6-7
Author(s):  
A. V. Crewe
Keyword(s):  
Normal Form ◽  
The Other ◽  
Resolving Power ◽  
Scanning Microscope ◽  
Conventional Microscope ◽  
Other Hand ◽  
Closing The Gap ◽  
Thermal Sources ◽  
Better Than ◽  
Transmission Microscope

We have become accustomed to differentiating between the scanning microscope and the conventional transmission microscope according to the resolving power which the two instruments offer. The conventional microscope is capable of a point resolution of a few angstroms and line resolutions of periodic objects of about 1Å. On the other hand, the scanning microscope, in its normal form, is not ordinarily capable of a point resolution better than 100Å. Upon examining reasons for the 100Å limitation, it becomes clear that this is based more on tradition than reason, and in particular, it is a condition imposed upon the microscope by adherence to thermal sources of electrons.

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