Alternative reaction conditions

Figure 11, Sequential conversion of coal to distillable products, char, and gas under alternate reaction conditions...

Taskinen and Nummelin (op. cit.) reported many other isomer equilibria in their paper. Most of these used cyclohexane as the solvent and I2 as the catalyst and so are not confounded by solvent effects. However, these authors noted that hydrogen atom transfer induced disproportionation (to form the aromatic benzene) dominates this reaction for the case of 49/50 isomerization and so they needed alternative reaction conditions. 

The introduction of these alternative approaches has permitted the direct trans-ferral and smooth integration of many versatile solution phase reagents from mainstream chemistry catalogues straight into practical protocols for use in com-hinatorial parallel hbrary generation thus broadening the amenable chemistry base. As with aU procedures it is the flexibihty and synthetic scope provided by these simple operations that has enhanced their utility as alternative reaction conditions and purification strategies. 

The development of alternative reaction conditions, including the use of more benign solvents and greater attention to the kinds of wastes released to the environment... 

Alternative reaction conditions are described in a synthesis of a 5,6-dihydronaphtho[l,2-6]pyran-4-one (406) (81CI(L)876) sodium hydride generates the anion from 2-acetyltetralone in DME. 

Developing alternative reaction conditions Design of reaction conditions that increase the selectivity of the prodnct and allow for dematerialization of the prodnct separation process. 

There are numerous ways by which these goals can be achieved and one that is currently under intensive scrutiny is the development of alternative reaction conditions and solvents or methodologies. Over the years biphasic catalysis has emerged as one of the most effective methods influencing all of the above criteria as volatile organic solvents are reduced or even completely eliminated from the process.2... 

Keywords Green chemistry alternative feedstocks benign reagents catalytic synthetic pathways natural processes biocatalysis alternative solvents safer chemicals alternative reaction conditions minimization of energy consumption... 

Alternative reaction conditions for efficiency and selectivity Minimization of energy consumption. 

Alternative reaction conditions, based on the use of solvents tliat have a reduced impact on hiunan health and the environment, increased selectivity and reduced wastes and emissions. 

Finally, it should be noted that FT should be considered as only one of the three steps in the conversion of natural gas into liquids, the other two being syngas generation and hydroprocessing.44 However, new concepts such as the combination of methane steam reforming and FT synthesis, in order to convert methane directly to hydrocarbons, have been explored.45 The idea seems to be operative at 573 K, using Ru and Co catalysts, but very low conversions are achieved.45 Thus, higher performance catalysts will have to be developed and the combination with alternative reaction conditions (such as supercritical fluids) merits consideration. 

A complex mixture resulted from cyclization of 123 with stannic chloride in dichloromethane-ethylene carbonate. The desired pentacyclic olefin 124 could be isolated in only 12% yield, and several alternate reaction conditions were no improvement. 

Alternative Reaction Conditions. The conditions that are used in synthesizing a chemical can have a significant effect on the pathway s overall environmental impact. Considerations of the amount of energy us by one process versus another is quite easily evaluated in economic terms but is not currently as easily evaluated in environmental terms. It appears that because of this difficulty in measurement, and not necessarily as a judgement on relative importance, that the majority of Green Chemistry research on reaction conditions has been centered around the substances utilized as part of those conditions. 

Alternative reaction conditions. Green Chemistry, 132-175 Alternative syntheses characterization, 223-227 computer generation of synthesis routes, 215-218... 

Alternative reaction conditions have since been developed to synthesize acylanthranils 36 from anthranilic acid. Treatment of 1 with benzoic acid and triphenyl phosphite in pyridine produced acylanthranil 36 (R = Ph) in 84% yield. It was not necessary to isolate acylanthranil 36. Instead the reaction mixture could be treated directly with aniline to give 37 (R = Ph) in 90% yield. Alternatively, it was found that treatment of N-acylanthranilic acid 27 (R = Me, Ph) with triphenyl phosphite and aniline in pyridine furnished 37 in 84% yield (R = Me) and 90% yield (R = Ph). Experimental evidence suggests that formation of 37 from acylanthranil 36 occurs via formation of an amidine as a result of attack of the aniline nitrogen on the C2 carbon of 36 followed by cyclization. ... 

Scheme 2.6. Control of syn anti Selectivity by Use of Alternate Reaction Conditions with Chiral Auxiliaries... 

Eco-efficiency is the efficiency with which ecological resources are used to meet human needs. It includes three scientific focus areas needed to achieve eco-efficiency. The three focuses, which are the same in the United States and Australia, are the use of alternative synthetic pathways, the use of alternative reaction conditions, and the design of chemicals that are less toxic than current alternatives or the design of inherently safer chemicals with regard to accident potential. 

A new synthesis of colchicine (108) utilizes the trifluoroacetic acid-induced conversion of (104) to (107) in 92% yield. This process probably proceeds via intermediates (105) and (106), which can be isolated when alternative reaction conditions are employed. 

Pummerer Reaction. In 1910, Pummerer reported that sulfoxides react with acetic anhydride to give 2-acetoxy sulfides (eq 21). The sulfoxide must have one a-hydrogen. Alternative reaction conditions include using trifluoroacetic anhydride and acetic anhydride. 

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