Ethers interesting/important

Crown and Macrocyclic Ethers.—Interesting and important studies continue to emerge, particularly in preliminary form, in this area of large-ring heterocyclics. Two important reviews have appeared. ... 

A Methylated dihydrofurans as donors. When studying the primary processes in the radiation chemistry of DNA, the dihydrofuran derivates are of special interest. As shown in Figure 10, enol-ethers are important transients in the heterolysis of the C4 radical in Additionally, enol-ether radical-... 

Potential Use. Processes using butylenes as feedstocks have been developed for a group of industrial chemicals that are not currendy produced by these processes or are produced only on a relatively small scale. Such chemicals are isoprene [78-79-5] maleic anhydride [108-31-6] acetic acid [64-19-7] and until recendy, methyl methacrylate and methyl tert-huty ether. These processes are of interest because they may emerge as important processes with suitable improvements, changes in product values, or development of new markets. 

The poly(vinyl ethers), whieh were first made available in Germany before 1940, are not of importance in the plastics industry but have applications in adhesives, surfaee coatings and rubber technology. Of the many vinyl ether polymers prepared, only those from the vinyl alkyl ethers and some halogenated variants are of interest. Two methods of monomer preparations may be used. 

Of somewhat greater technical interest are the addition compounds and the cellulose esters and ethers. Of the apparent addition compounds the most important is alkali cellulose produced by steeping cellulose in caustic soda and considered to be of general form (CgHioOs), (NaOH) ) rather than a sodium alcoholate compound. Alkali cellulose is a particularly important starting point in the manufacture of cellulose ethers. The ability of aqueous cuprammonium hydroxide solutions to dissolve cellulose appears to be dependent on addition compound formation. 

The processes used in the manufacture of morphine are believed to be still based on that described by the Scottish chemist Gregory,in 1833, with improvements devised by Anderson. A description has been published by Schwyzer, who also deals with the manufactme of codeine, narcotine, cotarnine, and the commercially important morphine derivatives, diamorphine (diacetylmorphine), and ethylmorphine (morphine ethyl ether). More recently Barbier has given an account of processes, based on long experience in the preparation of alkaloids from opium. Kanewskaja has described a process for morphine, narcotine, codeine, thebaine and papaverine, and the same bases are dealt with by Chemnitius, with the addition of narceine, by Busse and Busse, and by Dott. It is of interest to note that a number of processes for the extraction and separation of opium alkaloids have been protected by patent in Soviet Russia. ... 

Another issue important to the success of this chiral titanium reagent 31 was the discovery of a marked solvent effect. When the fumaric acid derivative is reacted with isoprene in the presence of 10 mol% of the titanium reagent 31 in toluene, poor optical purity results (36-68% ee). Interestingly the optical purity of the adduct greatly increased in the order benzene, toluene, xylenes, and mesitylene, with 92% ee obtained in the last. Mesitylene is difficult to remove, because of its high boiling point, and other solvents were screened in detail. As a result, the mixed solvent system toluene petroleum ether (1 1) was discovered to be very effective. 

On the other hand, quantitative extraction requires complete and exhaustive extraction and no material can be lost. To assure complete extraction when a food is analyzed for the first time in a laboratory, it is useful to carry out two or three extractions, pool the solvents, and keep separate the next extracts to verify the presence of carotenoids. Usually four to six extractions are enough to remove the carotenoids completely from a sample. The extraction can be carried out in a blender, vortex, or with a mortar and pestle. Accelerated solvent extraction (ASE), an important extraction technique in residue analysis, currently attracts interest due to its short duration, low level of solvent use, and high extraction yield. The average recoveries for all carotenoids with the exception of norbixin ranged from 88.7 to 103.3% using manual extraction and from 91.0 to 99.6% by ASE (70 bar and temperature of 40°C) both extractions were carried out with a mixture of MeOH, EtOAc, and petroleum ether (1 1 1). ... 

Various types of research are carried out on ITIESs nowadays. These studies are modeled on electrochemical techniques, theories, and systems. Studies of ion transfer across ITIESs are especially interesting and important because these are the only studies on ITIESs. Many complex ion transfers assisted by some chemical reactions have been studied, to say nothing of single ion transfers. In the world of nature, many types of ion transfer play important roles such as selective ion transfer through biological membranes. Therefore, there are quite a few studies that get ideas from those systems, while many interests from analytical applications motivate those too. Since the ion transfer at an ITIES is closely related with the fields of solvent extraction and ion-selective electrodes, these studies mainly deal with facilitated ion transfer by various kinds of ionophores. Since crown ethers as ionophores show interesting selectivity, a lot of derivatives are synthesized and their selectivities are evaluated in solvent extraction, ion-selective systems, etc. Of course electrochemical studies on ITIESs are also suitable for the systems of ion transfer facilitated by crown ethers and have thrown new light on the mechanisms of selectivity exhibited by crown ethers. 

The described approach to this pharmaceutically important class of compounds [324] was also utilized by Bonnet-Delpon and coworkers one year later [325]. Interestingly, these authors employed hexafluoroisopropanol (HFIP) as solvent and were able to perform the domino process without adding any extra Lewis acid catalyst such as InCl3 due to the acidic properties of HFIP (pKa = 9.3) [326]. Besides di-hydrofuran or dihydropyran, they have also used acyclic enol ethers. 

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