Cleaning and Selection

Clean and selective oxidation of dibenzyl and dibutyl sulphides to the corresponding... 

ADMET polymers are easily characterized using common analysis techniques, including nuclear magnetic resonance ( H and 13C NMR), infrared (IR) spectra, elemental analysis, gel permeation chromatography (GPC), vapor pressure osmometry (VPO), membrane osmometry (MO), thermal gravimetric analysis (TGA), and differential scanning calorimetry (DSC). The preparation of poly(l-octenylene) (10) via the metathesis of 1,9-decadiene (9) is an excellent model polymerization to study ADMET, since the monomer is readily available and the polymer is well known.21 The NMR characterization data (Fig. 8.9) for the hydrogenated versions of poly(l-octenylene) illustrate the clean and selective nature of ADMET. 

In summary, the Zn-Al and Zn-Ga based-hydrotalcites were found as very effective supports for docking a Rh(TPPTS)3Cl complex. The process was carried out via ionic exchange and occurred without any damage of die support structure or of the complex. The resulted catalysts were found to catalyze the cyclization of acetylenic carboxylic acids to the corresponding 5-membered ring heterocycles in good to excellent yields. The basic properties of the support also allow a clean and selective reaction of unsubstituted acetylenic carboxylic acids. 

The development in microwave chemistry has been remarkable during the last few years from the first reports in which, typically, domestic ovens were used to modern applications with state-of-the-art single-mode cavities. We believe that it is today possible today to develop robust microwave-assisted methods for nearly any reaction that needs an external heat source and we have proved it is possible to perform transition-metal catalyzed reactions very cleanly and selectively. 

A growing area of research is biocatalysis. The challenge is to use renewable agricultural products as feedstock and convert these feedstocks cleanly and selectively to chemicals using enzymes. Catalysis, bioengineering, and chemical engineering will be involved in development of new technologies. 

One common structural element of natural products exhibiting antibiotic properties is the incorporation of a (3-lactam moiety. This structural unit is somewhat labile. Because ozonation is generally recognized as a mild, clean, and selective method for oxidation of a compound, it can be considered an attractive synthetic transformation during the synthesis of antibiotics and their analogues. 

Cleavage via alkene metathesis is particularly useful because clean and selective scissoring of molecules is possible. Cleavage by metathesis can be performed either by cyclization during cleavage [95-101] (ring closing metathesis, RCM), inter-molecular metathesis [101] (cross metathesis), or intramolecular metathesis [95] (Scheme 6.1.23). 

The clean and selective formation of precatenate (F) deserves some comment. Of course, a homoleptic complex like (B) of Figure 2.22 could also have been formed. However, as shown in Figure 2.23, this would imply that... 

Zhu C, Ji L, Wei Y (2010) Clean and selective oxidation of alcohols with n-Bu NHSO catalyzed by ionic liquid immobilized TEMPO in ionic liquid [bmim][PEJ. Catal Commun 11 1017-1020... 

Reductions. The combination of trichlorosilane and tertiary amines (tri-n-propylamine, tri-n-butylamine used for the most part) has been used by Benkeser to effect some interesting reductions. Thus polyhalo compounds are reduced cleanly and selectively by this combination 1... 

An important preliminary to separation of mixed domestic plastics is the cleaning and selection operation. A simple method to perform this operation consists of a selection platform where a number of trained sorters separate the different types of plastics by visual assessment. Because manual selection is hable to human error, selection platforms may be equipped with detectors such as electronic devices to check the quality of the selected material. 

Several synthetically useful fluorinations of various organosulfur compounds with difluoroiodotoluene have been reported [13,24-26]. A clean and selective preparation of gm-difluorides 6 can be achieved by the... 

However, there have appeared a few reports on the formation of allenes 9 from 8 by the reaction of alkynes with halides. As one example, clean and selective formation of the allene 13 in good yield by the reaction of the aryl bromide 10 with 4-octyne (11) was reported. It is important to use ortfto-substituted bromides for the allene formation [1]. The reaction can be understood by f-R elimination from the alkenylpalladium species 12. Similar allene forming reactions have been reported [2-4]. At present, the allene formation has been observed only in reactions using dialkylacetylenes, and should be regarded as an exceptional process. 

Ru -pyridylamine complexes allowed the clean and selective photo-catalytic oxidation of various organic compounds, at room temperature, in water. Dinuclear Ru complexes have been also developed, in which one metal ion acts as the light harvester, and the other one acts as the oxidation catalyst. These systems can act as photocatalysts for the oxidation of a variety of substrates, i.e. alcohols, alkenes, and sulfides. ... 

A clean and selective method o-f synthesis o-f aromatic Isocyanates, use-ful on a laboratory scale, Is based on the carbonyl at I on at atmospheric pressure o-f aromatic azides[13] ... 

Replacement of the chemical step with a biocatalytic step is the first move toward green chemistry, which is followed by replacing the entire multiple-step process with a single fermentation process. Also, scientists have realized that biotechnology routes are inherently safe and mild and do not adversely impact the environment. Heterogeneous catalysis also appears to offer several advantages since the reactions are clean and selective. Also, the spent catalyst can be filtered and recovered for later use. 

Currently, the pharmaceutical industry presents many opportunities for electrolytic processes because of the need for new, clean and selective technologies moreover, the markets for products are for relatively low tonnages. Experience shows, however, that the move from a laboratory scale to production often requires the development of new technology and/or rethinking the relative importance of the criteria determining the process economics. 

A clean and selective method for the synthesis of aromatic isocyanates, useful on a laboratory scale, is based on the carbonylation at atmospheric pressure of aromatic azides (Scheme 2) [17] ... 

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