Synthesis of 5-tert-butyl-8,12,14-trimethyl- and 5-tert-butyl-8,12,14,16-tetramethyl[2.2]metacyclophane and their treatment with Lewis acids in benzene

2009 ◽  
Vol 2009 (7) ◽  
pp. 443-447 ◽  
Author(s):  
Tomoe Shimizu ◽  
Katsuhiko Hida ◽  
Takehiko Yamato
Keyword(s):  
Good Yield ◽  
Lewis Acids ◽  
The Other ◽  
Tert Butyl ◽  
Other Hand

Treatment of 5- tert-butyl-8,12,14,16-tetramethyl[2.2]MCP with AlCl3-MeNO2 in benzene led to trans- tert-butylation to afford 8,12,14,16-tetramethyl[2.2]MCP in good yield along with tert-butylbenzene. On the other hand, the same treatment of 5- tert-butyl-8,12,14-trimethyl[2.2]MCP led to transannular cyclisation reaction and isomerisation reaction to afford the corresponding strainless 2- tert-butyl-3a,6,8-trimethyl-3,3a,4,5,9,10-hexahydropyrene in good yield.

Notizen: Zur Reaktion von En-diolen mit Halogendisilanen.

1976 ◽  
Vol 31 (5) ◽  
pp. 694-695 ◽  
Author(s):  
E. Hengge ◽  
E. Brandstätter
Keyword(s):  
Good Yield ◽  
The Other ◽  
Other Hand ◽  
Membered Heterocycle

Alkalistilbenolate does not react, as expected, with dichlorotetramethyldisilane (1) to a six-membered heterocyclic, but the SiSi linkage is nucleophilic attacked by the oxygen and a five-membered heterocycle with only one Si-atom is formed. On the other hand, 1,2-dihydroxybenzene reacts with 1 to the new six-membered heterocycle in good yield.

STEROIDS AND RELATED PRODUCTS: XIX. THE SYNTHESIS OF 3,9,12,20-TETRAOXYGENATED 9,12-seco STEROIDS. PART III. 11-AZA STEROIDS. PART I

1962 ◽  
Vol 40 (11) ◽  
pp. 2153-2162 ◽  
Author(s):  
Ch. R. Engel ◽  
S. Rakhit
Keyword(s):  
Methyl Ester ◽  
Ethylene Glycol ◽  
Ethyl Acetate ◽  
Good Yield ◽  
Boron Trifluoride ◽  
Osmium Tetroxide ◽  
Periodic Acid ◽  
Boron Trifluoride Etherate ◽  
The Other ◽  
Other Hand

The smooth conversion of 3β-acetoxy-5α-pregnane-12,20-dione (IV), readily available from hecogenin (I), to Δ9(11)-3β,20β-diacetoxy-5α-pregnan-12-one (VIII) is reported. Ozonolysis of this product in ethyl acetate gave, in almost 90% yield, 3β-hydroxy-20β-acetoxy-9-oxo-9,12-seco-11-nor-5α-pregnan-12-oic acid (XI), further characterized by its ester derivatives XIa and XIb. The conversion of the seco acid XI to Δ8(9)-3β-hydroxy-20β-acetoxy-9-amino-9,12-seco-11-nor-5α-pregnen-12-oic acid lactam (12 → 9) (XII) and thence to Δ8(9)-N-acetyl-3β,20β-diacetoxy-11-aza-5α-pregnene (XIVa), the first 11-aza steroids to be known, is described. On the other hand, Δ9(11)-3β,20β-diacetoxy-5α-pregnen-12-one (VIII) is readily transformed to the 9α,11α-glycol VII with osmium tetroxide and thence, with periodic acid, to 3β,9α-dihydroxy-20β-acetoxy-11-oxo-11,12-seco-5α-pregnan-12-oic acid (X), characterized as the methyl ester Xa and diacetoxy methyl ester Xb, and easily converted to the acetoxy hydroxy keto dicarboxylic seco acid XIII. In the course of this work it is shown that, whereas ketalization of the saturated 12,20-diketone IV with ethylene glycol and boron trifluoride etherate gives a good yield of the 12-monoketal (in accordance with the reports of the literature), treatment of the analogous 16-unsaturated 12,20-diketone with the same reagents under the same conditions leads not to ketal formation but to addition of ethylene glycol in position 16.

scholarly journals Novel Convenient Approach to 6-, 7-, and 8-Numbered Nitrogen Heterocycles Incorporating Endocyclic Sulfonamide Fragment

Molecules ◽  
2020 ◽  
Vol 25 (12) ◽  
pp. 2887
Author(s):  
Oleksandr Shalimov ◽  
Eduard Rusanov ◽  
Oksana Muzychka ◽  
Petro Onys’ko
Keyword(s):  
Intramolecular Cyclization ◽  
Lewis Acids ◽  
Nitrogen Heterocycles ◽  
The Other ◽  
Other Hand ◽  
Convenient Approach ◽  
Imidoyl Chloride ◽  
Electrophilic Heterocyclization ◽  
Derivatives Of

A new effective method for the construction of nitrogen heterocycles incorporating endocyclic pharmacophore sulfonamide fragment, based on the use of easy accessible N-(chlorosulfonyl)imidoyl chloride, CCl3C(Cl)=NSO2Cl (1), has been developed. Thus, a reaction of 1 as bielectrophilic 1,3-C–N–S reagent with benzylamines that act as 1,4-N–C–C-C binucleophiles, affords respective 1,2,4-benzothiadiazepine-1,1-dioxides. On the other hand, 1 reacts with alkenyl amines with the formation of respective N-alkenyl amidines undergoing Lewis acids initiated intramolecular cyclization to afford derivatives of 1,2,4-thiadiazines and 1,2,4-thiadiazocines bearing a halomethyl group able for further functionalization. The first examples of electrophilic heterocyclization of the chlorosulfonyl group onto an alkenyl or alkynyl group have been revealed.

Acceleration and Aging

1954 ◽  
Vol 27 (1) ◽  
pp. 147-156 ◽  
Author(s):  
Adrien Haehl
Keyword(s):  
Synergetic Effect ◽  
Great Influence ◽  
The Other ◽  
Zinc Salt ◽  
Protective Agent ◽  
Protective Agents ◽  
Tert Butyl ◽  
Vulcanized Rubber ◽  
Other Hand

Abstract In a study of the protection of vulcanized rubber against aging by combinations of the zinc salt of mercaptobenzimidazole and “true” antioxygenic agents, it has been found that such combinations have a synergetic effect of considerable magnitude in the protection of vulcanizates which are accelerated by mercaptobenzothiazole. On the other hand, in the case of vulcanizates accelerated by diphenylguanidine, the effect is slight or even negligible. On the assumption, therefore, that the nature of the accelerator has a great influence on the effectiveness of the protective agents, the latter were classified with respect to the accelerators used. In this way it was established that bis-(2-hydroxy-3-tert-butyl-5-methylphenyl) methane, when employed alone is by far the best protective agent against the aging of vulcanized rubber accelerated by diphenylguanidine. In addition by combining this “true” antioxygenic agent with the zinc salt of mercaptobenzimidazole it was found that only slightly greater protection can be attained than is possible by the antioxygenic agent alone. Consequently in this case one should not speak of a synergetic effect. The experiments lead quite definitely to the conclusion that the mechanism of protection against aging when a deactivating agent is present depends upon whether the accelerator employed is mercaptobenzothiazole or diphenylguanidine.

Recent Advances in Radical Nitration Using tert-Butyl Nitrite

Synthesis ◽  
2020 ◽  
Vol 52 (06) ◽  
pp. 796-806 ◽  
Author(s):  
Si-Zhe Song ◽  
Youren Dong ◽  
Guo-Ping Ge ◽  
Qiang Li ◽  
Wen-Ting Wei
Keyword(s):  
Functional Groups ◽  
Reaction Mechanisms ◽  
Nitro Compounds ◽  
The Other ◽  
Tert Butyl ◽  
Mild Conditions ◽  
Recent Advances ◽  
Other Hand ◽  
The One

Nitro compounds serve as valuable intermediates for pharmaceuticals, agrochemicals, dyes, and polymers. In recent years, radical nitration using tert-butyl nitrite (t-BuONO) has attracted wide attention and desirable progress has been made. On the one hand, t-BuONO is a potential active nitro radical source and can react with various functional groups. On the other hand, as a green and novel nitration reagent, t-BuONO has relatively low price and can easily produce a radical under mild conditions, which undoubtedly provides a simple and efficient way for nitration reactions. To date, some important reviews are available that summarize the synthesis of nitro compounds. To the best of our knowledge, however, there is still no review that exclusively discusses the synthesis of nitro compounds using t-BuONO through a radical strategy. Therefore, this review aims to highlight the recent advances in radical nitration using t-BuONO as nitration reagent. The main progress in this area has been presented according to the type of reaction substrates. Special attention has been paid discussion of the reaction mechanisms and selected examples of substrates have been given. We hope this paper will be a useful reference and inspiration for those who are exploring the synthesis of nitro compounds using t-BuONO.1 Introduction2 Radical Nitration of Alkenes3 Radical Nitration of Aromatics4 Radical Nitration of Alkynes5 Radical Nitration of 1,n-Enynes6 Radical Nitration of Alkanes7 Summary and Perspective

scholarly journals PENGARUH PEMANGKASAN TANAMAN LADA DAN TAJARNYA TERHADAP HASIL

2020 ◽  
Vol 6 (3) ◽  
pp. 55
Author(s):  
USMAN DARAS ◽  
PASRIL WAHID
Keyword(s):  
Good Yield ◽  
The Other ◽  
Research Station ◽  
Plot Size ◽  
Other Hand ◽  
Split Plot ◽  
Main Plot ◽  
Plot Design

<p><strong>The effect of living post and pepper vines primings on the pepper yield</strong></p><p>To obtain good yield of pepper, farmers fequently apply various treatments to their crops, including pruning of the pepper vines and or their living post. Studies on the aspects of the pruning ae however very limited. Therefore a ield experiment was conducted to investigate the effects of pruning of pepper vines and their living post on the pepper yield. The experiment was carried out at Sukamulya Research Station, Sukabumi. A split plot design with three rcplicaties was used. The main plot was the pruning of living post, and the sub plot was the pruning of pepper vines Plot size was 20 plants per plol wilh spacing of 2.5 m x 2.5 m Results showed that there was signiicant interaction between the pruning of living post and pepper vines. The pruning of living post may be carried out either 3 times (October, January and April) or twice (October and January) a year. However. If the pruning of the living post is carried out 3 times per year, Ihe vine would be pruned once a year or not at all. On the other hand, if the pruning of living post is carried out twice a year, the pepper vines would be pruned 6 times a year.</p>

scholarly journals The Acid-Base Through-the-Cage Interaction as an Example of an Inversion in a Cage Isomerism

Symmetry ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 1291
Author(s):  
Jan Cz. Dobrowolski ◽  
Sławomir Ostrowski
Keyword(s):  
Lewis Acids ◽  
Lewis Base ◽  
The Other ◽  
Acid Base ◽  
Component System ◽  
Other Hand

We define a new inversion in a cage isomerism (ic): X@C⋯Y₪icY@C⋯X, (₪ is the isomerism relation) as an isomerism in the three-component system of molecules X, Y, and a cage C, in which one of the molecules is located inside and the other outside the cage. The ic isomerism is similar to the endo-exo one, which occurs only if either the interior or exterior of C is empty. By contrast, ic occurs only if neither the interior nor the exterior of C is empty. We also discuss the other closely related types of isomerisms are also discussed. Calculations of the XH⋯NH3@C60 and NH3⋯HX@C60ic isomers were performed at the ωB97XD/Def2TZVP level. The calculated energies demonstrated that the systems with the HX acid outside (X = F, Cl) and the NH3 base inside the cage, XH⋯NH3@C60, are more stable than their ic isomers, NH3⋯HX@C60, by about 4–8 kcal/mol. This is because NH3 is more stabilized inside the cage than HX (a matter of 6.5 kcal/mol). In the studied systems and subsystems, the HX molecules are Lewis acids and the NH3 molecule is always a Lewis base. The C60 molecule with HX inside or outside the cage is also an acid for the NH3 base positioned outside or inside the cage. On the other hand, the C60 cage is truly amphoteric because it is simultaneously an acid and a base.

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.

Life Beyond 1MeV

1980 ◽  
Vol 38 ◽  
pp. 30-33
Author(s):  
K.H. Westmacott
Keyword(s):  
Electron Microscopy ◽  
Past Experience ◽  
The Other ◽  
Good Case ◽  
Other Hand ◽  
The U.S

Life beyond 1MeV – like life after 40 – is not too different unless one takes advantage of past experience and is receptive to new opportunities. At first glance, the returns on performing electron microscopy at voltages greater than 1MeV diminish rather rapidly as the curves which describe the well-known advantages of HVEM often tend towards saturation. However, in a country with a significant HVEM capability, a good case can be made for investing in instruments with a range of maximum accelerating voltages. In this regard, the 1.5MeV KRATOS HVEM being installed in Berkeley will complement the other 650KeV, 1MeV, and 1.2MeV instruments currently operating in the U.S. One other consideration suggests that 1.5MeV is an optimum voltage machine – Its additional advantages may be purchased for not much more than a 1MeV instrument. On the other hand, the 3MeV HVEM's which seem to be operated at 2MeV maximum, are much more expensive.

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