Saccharin intermediates

Fibrous stmctures represent a grain refinement of columnar stmcture. Stress-reHeving additives, eg, saccharin or coumarin, promote such refinement, as do high deposition rates. These may be considered intermediate in properties between columnar and fine-grained stmctures. 

In addition to a continued increase in the number of use patents in these fields, a new use of xanthates as inhibitors of fertiliser nitrogen transformation in soil has been reported, as well as the use of certain metal xanthates as color developers for image-recording materials (113,114) (see Fertilizers Color photography). For several years, sodium isopropyl xanthate was used as an intermediate in the manufacture of saccharin (see... 

When saccharin is treated with diethyl phosphorothiolothionate, the 3-ethylmercapto compound is obtained, rather than the expected organophosphorus compound (77 ACS(B)460). Treatment of saccharin with phosphorus pentoxide and amines gives 3-(substituted-amino)-1,2-benzisothiazole 1,1-dioxides, via an intermediate phosphate (81ZN(B)1640). Reduction of saccharin with zinc and hydrochloric acid gives 2,3-dihydro-l,2-benzisothiazole 1,1-dioxide, the method being used to estimate saccharin in foodstuffs (75MI41701). 

Various saccharin derivatives 260 have been prepared by chromium (VI) oxide catalyzed H5IO6 oxidation of substituted ort/ro-toluenesulfonamides 259 <06T7902>. The reaction presumably proceeds through a benzylic radical intermediate 261 generated from the... 

Chemical/Physical Sulfometuron-methyl is stable in water at pH values of 7 to 9 but is rapidly hydrolyzed at pH 5.0 forming methyl-2-(aminosulfonyl) benzoate and saccharin. When sulfometuron-methyl in an aqueous solution was exposed to UV light (k = 300-400 nm), it degraded to the intermediate methyl benzoate which then mineralized to carbon dioxide (Harvey et ah, 1985). 

Saccharinic acid formation has been studied for several years. The four-step reaction proceeds rapidly in alkaline solution because of basic catalysis, particularly in the last two steps. Initially formed is an enediol that can undergo j8-elimination of a functional group, usually a hydroxyl group. The final two steps involve tautomerization to an a,j8-dicarbonyl intermediate followed by a benzilic acid rearrangement. This sequence is shown in Scheme 6 for the formation of the a- and j8 -xylometasac-charinic acids (30) by way of 3-deoxy-D-g/ycero-pentos-2-ulose (29). 

This benzilic acid type of rearrangement is the result of the action of alkali on the dicarbonyl compound, and is accelerated by calcium ions. The formation of saccharinic acids by the action of aqueous alkali on sugars is very well known 82,84,92 however, if ammonia is present, very little8 or no production of saccharinic acid has been reported. The reaction of the intermediate carbonyl compounds with ammonia is faster than the benzilic acid type of rearrangement to give saccharinic acid, and, hence, substituted imidazoles are formed, as illustrated in Scheme 9. 

Toluene-o-sulphonamide is an intermediate in the synthesis of saccharin (Expt 6.42). Upon oxidising toluene-o-sulphonamide with potassium permanganate in alkaline solution, the sodium salt of o-sulphonamidobenzoic acid is formed, which on acidification with concentrated hydrochloric acid passes spontaneously into the cyclic imide of o-sulphobenzoic acid or saccharin. Saccharin itself is sparingly soluble in cold water, but the imino hydrogen is acidic and the compound forms a water-soluble sodium salt. The latter is about 500 times as sweet as cane sugar. 

G. Machell and G. N. Richards, Mechanism of saccharinic acid formation. Part II. The a, /3-dicarbonyl intermediate in formation of D-glucoisosaccharinic acid, J. Chem. Soc., (1960) 1932-1944. 

It has been postulated (37) that lactulose is formed from lactose by the Lobry de Bruyn and Alberda van Ekenstein transformation, whereby glucose is isomerized to fructose via an enol intermediate. In turn, two mechanisms have been proposed for the degradation of this intermediate (38)- One involves the addition of a proton to the enediol resulting in epimeric aldoses and the original ketose, while the other involves 8-elimination to yield galactose and saccharinic acids. The authors experimental data would tend to better support the second pathway. 

The 1-deoxyosone represents the most elusive of the three intermediates, but also the most important from the standpoint of food flavor and aroma production. A large number of methyl-containing furanones, pyrones and related compounds are found in food preparations that are consistent with having been formed from this intermediate. A synthesis of this material was reported some years ago by Isuzu, et al. (10), but the yields were very low and the product was not well characterized. The workers reported that the compound gave one of the two reported isomers of "saccharinic acid", the expected degradation product in alkaline solution, along with fragmentation products. This material will be addressed (vide infra) in a later section. 

The major use of phthalic anhydride is for ester derivatives used as plasticizers in the manufacture of flexible poly(vinyl chloride), e.g., wallpaper. The largest volume plasticizer is the di(2-ethylhexyl)phthalate. Other uses of phthalic anhydride are for unsaturated polyester and alkyd resins, for dye intermediates, and for isatoic anhydride (for the production of saccharin). 

A-Halogenoalkyl saccharins (56)103,153,200 are key intermediates for the preparation of symmetrically substituted ethylenediamines, ethanolamines, and homologs120 through direct exchange with an amine (57) or with acetate, in the latter case followed by Abe s procedure. (57) is also obtained from alkylation of 1 with alkyl or dialkylaminoalkyl halides.106,119. 

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