Waste-free

Magnetic separation for ferrous materials eddy-current separation for aluminum electrostatic separation for glass from wastes free of ferrous and aluminum scrap magnetic fluid separation for uouferrous materials from processed wastes... 

Benson and Ponton (1993) and Ponton (1996) have speculated on the ultimate results of continuing efforts for process minimization. They envision a twenty-first century chemical industry totally revolutionized by technological innovation, automation, and miniaturization. Small, distributed manufacturing facilities would produce materials on demand, at the location where they are needed. Raw materials would be nonhazardous, and the manufacturing processes would be waste free and inherently safe. While their vision of future technology is speculative, we are beginning to see progress in this direction. 

For example, consider organic reactions in water. Beyond a general methodology for carrying out catalytic conversions in H20 mediated by doped ORMOSIL in the presence of a modest amount of surfactant,19 another recent method for the waste-free oxidation of alcohol affords high yields of commercially valued carbonyl compounds in water with complete selectivity and remarkable stability.20... 

G. Palmisano, R. Ciriminna and M. Pagliaro, Waste-Free Electrochemical Oxidation of Alcohols in Water, Adv. Synth. Catal., 2006, 348, 2033. 

Lymberidi, E. (2001). Towards Waste-Free Electrical and Electronic Equipment. The examples are cited from Tadatomo Suga, University of Tokyo, Good practice on the substitution of heavy metals in... 

The a-alkylation of enolates derived from ketones with alkyl halides is a very important and frequently used method for forming new carbon-carbon bonds in organic synthesis [40]. Yet, if the a-alkylation of enolates derived from ketones with alkyl halides can be replaced by the direct reaction of ketones with alcohols, this method would provide a very useful waste-free, green route to a-alkylation, producing no side products other than water. 

The catalytic preparation of esters and amides under mild and waste free reaction conditions using readily available starting materials is a desirable goal. The first redox process of this type using heterocyclic carbenes was reported by Castells and co-workers in 1977 in which aldehydes were oxidized to esters in one-pot in the presence of nitrobenzene [104], Furfural 169 is converted into methyl 2-furoate 170 in 79% yield Eq. 15. Nitrobenzene is the presumed stoichiometric oxidant for the oxidation of the nucleophilic alkene XXX to the acyl azolium XXXI by successive electron transfer events. The authors observe nitrosobenzene as a stoichiometric byproduct. This type of reactivity is also observed when cyanide is used as the catalyst. Miyashita has expanded the scope of this transformation using imida-zolylidene carbenes [105-107]. 

TEMPO has been structurally modified to bring about new selectivities. Highly efficient anionic water-soluble TEME<), oil-in-water nanoemulsion containing TEME for oxidation of alcohols and a waste-free system were developed. Especially, the sterically less crowded azabicyclo-Af-oxyls oxidized /-menthol to Z-menthone with much higher efficiencies than TEME O (equation 23). ... 

Pure soHd-state reactions are more frequently waste-free than melt reactions with increased risk of incompleteness or side reactions. We select here only... 

Eliminations belong to one of the most diverse reaction types [76] and numerous solvent-free pyrolyses (sometimes quantitative melt reactions) provided useful syntheses [58,81-87]. However, quantitative solid-state eliminations are rare (examples are found in the halogenations of 110,112, and 114 (Scheme 12)). If an elimination reaction cannot be performed purely thermally or photo-chemically, usually a catalyst or other auxiliary has to be added and it is then no longer waste-free. 

Solid tertiary amines and imines may be quantitatively alkylated by gas-solid and solid-solid techniques. Methylation of quinuclidine (176) to give the methoiodide 177 is achieved waste-free by exposure of 176 to a stoichiometric amount of methyl iodide vapor (Scheme 23). Difficulties with the disintegration of the crystals of 177 from those of 176 (reaction step 3) are overcome by ultrasound treatment from a cleaning bath at 20 °C [22]. Numerous applications of this technique to tertiary amines can be envisaged. However, solid Troeger s base (with interlocked layers, i.e., no possibility for molecular migrations) is not alkylated by methyl iodide vapor unless an excess of the vapor is applied to induce intermediate (partial) liquefying of the solid [22]. 

Free radicals may substitute C-H bonds. Gaseous NO2 (0.3 bar) has been tested with solid barbituric acids (40a-c). Reactions with 100% yield arise after 4 h exposure and the dried products (80 °C) assume the acz-nitro forms 258a-c [19] (Scheme 37). A very large field for preparative use appears to be opened with these and related waste-free reactions. The couple product N2O3 can be collected for further use. 

Similarly, solid cyclic imides are attacked by gaseous aliphatic amines and lead to open-chain diamides. For example, 269a-c react with ethylamine gas to give a 100% yield of the diamide 270, which can be quantitatively cyclized to the JV-ethylimide 271 by the action of gaseous HCl [12]. As expected, the solid alicyclic imides 272 behave correspondingly and yield the bis-amides 273 in an easy waste-free procedure [12] (Scheme 39). 

A very old gas-solid bromination of tyrosine (280) [97] has been revisited and it gave a quantitative yield for the reaction of rac-280 [22]. The doubly bromi-nated hydrobromide rac-281 is spectroscopically pure after removal of included gases at 50 °C in a vacuum. Quite spectacular is the specific and quantitative waste-free gas-solid tetrabromination of tetraphenylethylene (282), which shows some signs of autocatalysis and requires rotation of the flask around a horizontal axis at room temperature for 12 h as the reactant and product gases require mixing [60]. The isomer-free tetrabromide 283 is an attractive starting point for dendrimer syntheses and inclusion studies (Scheme 40). Also 4-bro-mo antipyrin hydrobromide is quantitatively obtained from antipyrin(hydro-bromide) and bromine vapor [22]. 

Equally popular are azo couplings of diazonium salts that keep the nitrogen atoms in the product. The solid-solid version is very suitable with appropriate phenols such as 296 and 299. The waste-free and quantitatively obtained azo dye salts can be neutralized. The free dyes have the hydrazono structure (297, 298) or the azo structure (300) [99-100] (Scheme 45). The prescription should be carefully followed for safety reasons ... 

An interesting synthetic approach to cyclic enamine ketones is provided by waste-free and quantitative solid-state reaction of the anilines 236 with cyclic 1,3-diketones such as 332 or enolized 334 (Scheme 52). The enamine ketones 333c-h are quantitatively obtained in the solid state by milling at room temperature. The melt reaction (80 °C) for 333a is not quantitative, but 333b arises with 100% yield from the melt reaction [10]. All of the solid-state reactions give 100% yield, as usual. 

Electron-poor alkenes are suitable starting points for Michael additions. For example, the arylidene malononitrile 363 adds quantitatively to solid dimedone (255) upon milling at 80 °C followed by heating of the yellow powder to 100 °C. The initial Michael adduct 364 is not isolated, as it cyclizes in the solid state to give the pyrone 365 with 100% yield [107] (Scheme 58). The potentials for waste-free solid-state chemistry are manifold indeed and deserve further exploration. 

The solid-state interaction of enamines (428, 333a) with trans-l,2-diben-zoylethene (87) provides quantitative yields of the pyrrole derivatives 445 or 446 [140]. These remarkable 5-cascades consist of initial vinylogous Michael addition, enol/keto tautomerism, imine/enamine tautomerism, cyclization, and elimination, all within the crystal without melting. A waste-free extraordinary atom economy is achieved that cannot nearly be obtained in solution. The milling times are unusually long here (3 h) but it s certainly worth the effort... 

The catalysts are prepared as described previously. [6] The templating solution consists of a solution of n-dodecylamine (5.09 g) in aqueous ethanol (53 ml water and 46 ml ethanol). To this is added a total of 0.1 mol silane. The reaction is allowed to proceed for 18 h at room temperature. After filtration and extraction of template with ethanol, the material is filtered and dried. The filtrate from the preparation is generally free of unreacted silanes, indicating that all the silanes are condensed, a fact borne out by the excellent agreement between theoretical and experimental composition. The template and the ethanol can both be recovered pure (the template with 99% efficiency). Both can be reused, as can the templating solution. This means that the process is essentially waste-free[7],... 

Keywords 1,1-diarylethylene, HC1, catalysis, linear dimerization, head-to-tail, waste free, gas-solid reaction, 1,1,3,3-tetraaryl-l-butene... 

Keywords ninhydrin, dimedone, aminocrotonate,, cyclization, cascade reaction, waste-free, solid-solid reaction... 

Keywords anilines, benzaldehydes, condensation, waste-free, azomethines... 

Keywords barbituric acid, nitrogen dioxide, nitration, waste-free, gas-solid reaction... 

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