Solid decarboxylation

The seven-membered CN3S3 ring, another ten 7r-electron system, was first obtained as the ester 12.19 (R = COaMe), which is a minor product of the reaction of S4N4 with dimethylacetylene dicarboxylate. It has a planar structure with bond lengths that indicate delocalization. The parent 1,3,5,2,4,6-trithiatriazepine 12.19 (R = H) is obtained as a colourless solid by carefully heating the ester with aqueous HCl followed by decarboxylation. ... 

The predominant gaseous products of the decomposition [1108] of copper maleate at 443—613 K and copper fumarate at 443—653 K were C02 and ethylene. The very rapid temperature rise resulting from laser heating [1108] is thought to result in simultaneous decarboxylation to form acetylene via the intermediate —CH=CH—. Preliminary isothermal measurements [487] for both these solid reactants (and including also copper malonate) found the occurrence of an initial acceleratory process, ascribed to a nucleation and growth reaction. Thereafter, there was a discontinuous diminution in rate (a 0.4), ascribed to the deposition of carbon at the active surfaces of growing copper nuclei. Bassi and Kalsi [1282] report that the isothermal decomposition of copper(II) adipate at 483—503 K obeyed the Prout—Tompkins equation [eqn. (9)] with E = 191 kJ mole-1. Studies of the isothermal decompositions of the copper(II) salts of benzoic, salicylic and malonic acids are also cited in this article. 

Decarboxylation of p-lactones (see 17-27) may be regarded as a degenerate example of this reaction. Unsymmetrical diacyl peroxides RCO—OO—COR lose two molecules of CO2 when photolyzed in the solid state to give the product RR. Electrolysis was also used, but yields were lower. This is an alternative to the Kolbe reaction (11-37). See also 17-29 and 17-40. 

Kaeriyama et al. [15] reported the Ni(0)-catalyzed coupling of 1,4-dibromo-2-methoxycarbonylbenzene to poly(2-methoxycarbonyl-l,4-phenylene) (4) as a processable PPP precursor. The aromatic polyester PPP precursor, 4, is then saponified to carboxylated PPP (5) and thermally decarboxylated to 1 with CuO catalysts. However, the reaction conditions of the final step are quite drastic and cannot be carried out satisfactorily in the solid state (film). 

The product obtained from this type of decarboxylation is reported to contain only about 5% of /ra s-stilbene.5 A sample made according to the above directions can be treated with bromine in carbon tetrachloride at room temperature in the dark to give an 80-85% yield of the d/-dibromide which arises from trans addition to cw-stilbene. The meso-dibromide, which is very soluble and easily separated, is obtained only to the extent of 10% or less. Part of this latter product may arise from the action of bromine atoms on cw-stilbene rather than from trans addition to tfnms-stilbene. The cu-stilbene prepared by this method is readily and completely soluble in cold absolute ethanol. It freezes solid at about —5°. Its ultraviolet absorption coefficient (8) is 1.10 X 104 at 274 mil and 8.7 X 103 at 294 mp, quite different from h-aws-stilbene. 

As pointed out previously, controlled degradation reactions are very difficult with aliphatic or alicyclic hydrocarbons, and most of the relabeling work has been concentrated on aromatic reaction products. Procedures have been extensively described by Pines and co-workers (e.g., 97, 96, also 87, 89-98, 95, 98). For the present purpose, it suffices to note that the 14C contents of the methyl side-chains and the rings in aromatic reaction products are readily estimated by oxidation of the methyl to carboxyl, followed by decarboxylation, while ethyl side-chains may be oxidatively degraded one carbon atom at a time. Radiochemical assays may be made on CO2 either directly in a gas counter, or after conversion to barium carbonate, while other solid degradation intermediates (e.g., benzoic acid or the phthalic acids) may be either assayed directly as solids or burned to CO2. Liquids are best assayed after burning to CO2. 

Mercuric carboxylates, which decarboxylate by a chain mechanism when initiated by peroxides, also decarboxylate under UV irradiation (123,128,129,131-140,142,144-146,153-155). In addition, decarboxylation was observed for mercuric benzoate and mercuric a-naphthoate (123). Side reactions [Eqs. (24), (25), (109)] observed in peroxide initiated reactions also occurred on UV irradiation, and mercurous salt formation [Eq.(24)] was more extensive under the latter conditions. Decarboxylation giving methylmercuric acetate occurred on irradiation of mercuric acetate in aqueous solution and is considered to be of environmental significance (156,157). Stepwise decarboxylation giving (CF3)2Hg occurred on irradiation of solid mercuric trifluoroacetate at -196° C (158), but, at 20° C, trifluoromethyl radicals diffused from the solid and dimerized (158). No other diorganomercurial has been formed by radical decarboxylation, and the reaction is not preparatively competitive with the thermal decarboxylation synthesis of (CF3)2Hg (26,27) (Section III,A). 

The potential of the microwave-enhanced decarboxylation route in the radioactive waste area is immediately apparent - washing the tritium waste with a protic solvent leads to exchange of the labile tritium. The solvent can then be used with one of the carboxylic acids mentioned above and after the microwave-enhanced decarboxylation the waste is now in the form of a solid (greatly reduced volume) which may have some further use. 

The resulting solution is cooled to 0° and decomposed by careful addition of 500 ml. of 102V hydrochloric acid. The mixture is transferred to a separatory funnel, the aqueous phase is separated, and the toluene layer is extracted with two 250-ml. portions of 102V hydrochloric acid. The aqueous extracts are combined and heated under reflux for 15 hours to effect decarboxylation. The hot, dark-colored solution is treated with 10 g. of activated charcoal, filtered, and evaporated to dryness under reduced pressure. The residue is washed into a separatory funnel with 300 ml. of water. The solution is treated with saturated aqueous potassium carbonate solution until it is alkaline to litmus the carbonate solution must be added very carefully to prevent excessive foaming. Solid potassium carbonate is added until a thin slurry is obtained, and the slurry is extracted with four 400-ml. portions of ether. The combined ether extracts are dried for at least 60 minutes over calcined potassium carbonate and then filtered. 

To a solution of 1.84 g Na metal in 60 ml ethanol at 5-10° add, over Vi hour with vigorous stirring a mixture of 0.08 M ethyl azidoacetate and 0.02 M 2 (or 2,5 2,3 etc. but not 6) substituted benzaldehyde and continue stirring at 5-10° until nitrogen evolution ceases (about V2-I hour) then stop immediately and rapidly evaporate in vacuum Vi the ethanol (keep temperature below 30°). Basify the solution with solid NH CI, dilute with 500 ml water and extract 3 times with ether. Filter, wash with water to neutrality and dry, evaporate in vacuum the ether (or can dissolve the residue in petroleum ether, or 1 1 petroleum ether.benzene for methoxy compounds, and filter through silica gel) to get the ethyl-alpha-azidocinnamates (1) in about 50% yield. Store in freezer until used in next step. Dissolve 1 g (I) in 100 ml p-xylol and reflux 10 minutes. Evaporate in vacuum (or add 5 ml pentane, filter, evaporate in vacuum) to get about 90% yield of the 4 substituted-2-car-bethoxyindole which can be decarboxylated as described elsewhere here. 

Dissolve 4 g glyoxylic acid monohydrate in 220 ml water and add with stirring to a solution of 10 g 4,5, or 6 methoxy-tryptamine-HCl in 80 ml water. Adjust pH to 4 with 10% KOH and stir five hours at room temperature. Filter and wash with water to get about 4.5 g precipitate. Melt to decarboxylate or to 4 g precipitate add 30 ml concentrated HCI and 100 ml water and heat at 65° one hour. Add water to dissolve the solid and add excess 10% KOH. Filter to get the title compound or analog. 

While much attention has been paid to the chemistry of cyclodextrin complexes in solution, there have been relatively few studies of their solid-state reactions. One such reaction is the decarboxylation of phenylethylmalonic acid, 155. In solution this is catalyzed by fj-cyclodextrin, and yields racemic 2-phenylbutyric acid, 156 (230). The malonic acid forms a crystalline 1 1 complex with p-cyclodextrin in which decarboxylation occurs at a much lower temperature than in the crystalline diacid. Interestingly, the product formed in the clathrate reaction is nonracemic, the optical yield being 7%. 

Alternative procedures for the generation of dichlorocarbene and dibromocarbene under phase-transfer catalysed conditions are also available. Where the reactive substrate is labile under basic conditions, the thermal decomposition of solid sodium trichloroacetate or bromoacetate under neutral conditions in an organic solvent is a valuable procedure [10-12], The decarboxylation is aided by the addition of a quaternary ammonium salt, which not only promotes dissolution of the trihaloacetate anion in the organic solvent, but also stabilizes the trihalomethyl anion. Under optimum reaction conditions, only a catalytic amount of the quaternary ammonium salt is required, as a large amount of the catalyst causes the rapid generation of the dichlorocarbene with resultant side reactions. 

True alkaloids derive from amino acid and they share a heterocyclic ring with nitrogen. These alkaloids are highly reactive substances with biological activity even in low doses. All true alkaloids have a bitter taste and appear as a white solid, with the exception of nicotine which has a brown liquid. True alkaloids form water-soluble salts. Moreover, most of them are well-defined crystalline substances which unite with acids to form salts. True alkaloids may occur in plants (1) in the free state, (2) as salts and (3) as N-oxides. These alkaloids occur in a limited number of species and families, and are those compounds in which decarboxylated amino acids are condensed with a non-nitrogenous structural moiety. The primary precursors of true alkaloids are such amino acids as L-ornithine, L-lysine, L-phenylalanine/L-tyrosine, L-tryptophan and L-histidine . Examples of true alkaloids include such biologically active alkaloids as cocaine, quinine, dopamine, morphine and usambarensine (Figure 4). A fuller list of examples appears in Table 1. 

The solid phase synthesis of quinazoline 114 was reported by Abell and co-workers, in which a traceless linker was utilized <99TL1045>. The key step in this procedure was the removal of the desired quinazoline from the resin with concurrent decarboxylation to produce 114 in 69% yield from 113. 

The majority of publications on transesterification catalyzed by solid acids have focused on the reaction of 3-keto esters. Transesterification provides an alternative route to synthesize these kinds of esters since direct preparation from P-keto acids is not a good option given that they can easily undergo decarboxylation. Table 11 provides a review of results in the literature relating to the transesterification of P-keto esters with alcohols. 

However, this achievement was then marred by an unfortunate error. The calcium salt of 4-fluorobenzoic acid was heated in admixture with calcium hydroxide, and fluorobenzene was claimed to be formed by decarboxylation. Later, it was shown16 that the product, a solid, was phenol. It had been analyzed only for carbon and hydrogen content an early warning to all workers in fluorine chemistry of the need for quantitative assays for fluorine in their products. Being more activated than fluorobenzene towards nucleophilic attack, the fluorobenzoate anion itself probably lost fluorine before decarboxylation occurred. A benzyne-type process seems to be a less likely reaction pathway. 

W.C.Fernelius, ChemRevs 12, 67(1933) 20,413(1937) 3)Franklin(l935), 54-5 4)Inorg-Synth 1(1939) 74-7 2(1946), 128-35 Nitramide or Nitroxyl amide, 02N.NH2, raw 62.03, N 45.1755. Wh solid, mp 72-5° with de-compn puffs off on rapid heating. Sol in w (slowly dec) and in common solvents, except petr ether. Was first, prepd in 1890 by Mathieu-Plessy but not properly identified. Thiele Lachman prepd it in 1894(Refs 1,2 3) from nitrourethane,OaN.NHCOO.CaHs, and described its props. Since then nitramide was prepd by various investigators, mostly by hydrolysis and decarboxylation of potassium —N —... 

The oxazolidine-2,5-dione heterocycle, perhaps better known as the N-carboxyanhydride of an amino acid, has been incorporated employing a modification of chloromethylated poly(styrene) (192) (76USP3985715). The reaction sequence involved utilization of a masked amino acid, ethyl acetamidocyanoacetate (205). The amino acid was liberated in a subsequent hydrolysis/decarboxylation step (Scheme 98). The cyclized, IV-carboxyanhydride-functional resins (206) were reported to be useful in solid phase peptide synthesis and as supports for enzyme immobilization. 

The adducts a-lactylthiamin and a-lactylthiamin diphosphate have both been synthesized.84 98 100 As long as a-lactylthiamin is kept as a dry solid or at low pH, it is stable. However, it decarboxylates readily in neutral solution (Eq. 14-21). Decarboxylation is much... 

The solid has a tendency to assume a semi-plastic consistency, but the size of the mass decreases as decarboxylation occurs. 

Results obtained for two mixed plastics are summarized in Table 4. A balance exists between process temperature, plastics feed rate, and product yields (67). For example, lower temperatures increase wax formation due to incomplete depolymerization. Slower feed rates and increased residence times reduce wax formation and increase the yield of liquids. The data summarized in Table 4 illustrate that the addition of PET to a HDPE PP PS mixture changes the performance of the Conrad process. Compared to the reference HDPE PP PS mixture, increased amounts of solids are formed. These are 95% terephthalic acid and 5% mono- and bis-hydroxyethyl esters. At higher temperatures, apparendy enough water remains to promote decarboxylation. 

SYNTHESIS This compound has been made industrially by a number of routes, with the reduction of benzyl cyanide and the decarboxylation of phenylanaline being the more important. It is offered in the catalogs of all the major chemical supply houses for a few pennies per gram. It is a very strong base with a fishy smell, and rapidly forms a solid carbonate salt upon exposure to the air. It is a natural biochemical in both plants and animals. 

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