Sulfinic acids synthesis

Ueno and coworkers49 have developed a procedure for the synthesis of chiral sulfinic acids. Treatment of (R)-( + )-23 with disulfide 24 and tributylphosphine in THF gave (S)-( — )-25. Compound 25 was oxidized with potassium permanganate to the sulfone, which was then reduced to the sulfinic acid, (S)-( — )-26, by treatment with sodium borohydride. Conversion of 26 or an analog to an ester would lead to diastereomers. If these epimers could be separated, then they would offer a path to homochiral sulfoxides with stereogenic carbon and sulfur atoms. 

The most commonly employed routes for the preparation of the / -sulfatoethylsulfone group, which is the essential structural feature of vinylsulfone reactive dyes, are illustrated in Scheme 8.5. One method of synthesis involves, initially, the reduction of an aromatic sulfonyl chloride, for example with sodium sulfite, to the corresponding sulfinic acid. Subsequent condensation with either 2-chloroethanol or ethylene oxide gives the / -hydroxyethylsulfone, which is converted into its sulfate ester by treatment with concentrated sulfuric acid at 20 30 °C. An alternative route involves treatment of an aromatic thiol with 2-chloroethanol or ethylene oxide to give the /Miydroxyethylsulfonyl compound which may then be converted by oxidation into the /Miydroxyethylsulfone. 

Enzymes of the pepsin family rarely catalyze the hydrolysis of esters, with the exceptions of, for example, esters of L-/3-penicillactic acid and some sulfinic acid esters. Under suitable conditions, i. e., low pH, high enzyme concentration, and formation of an insoluble peptide, aspartic peptidases are able to catalyze the synthesis of peptides [71] [72],... 

Sulfur compounds with divalent sulfur functionalities are much more prone to dioxirane oxidation on account of their higher nucleophilicity compared to the above-presented oxygen-type nucleophiles. Examples of this type of dioxirane oxidation abound in the literature. Such a case is the oxidation of thiols, which may be quite complex and afford a complex mixture of oxidation products, e.g. sulfinic acids, sulfonic acids, disulfides, thiosulfonates and aldehydes , and is, therefore, hardly useful in synthesis. Nevertheless, the oxidation of some 9i/-purine-6-thiols in the presence of an amine nucleophile produces n >( -nucleoside analogs in useful yields (equation 19). This reaction also displays the general chemoselectivity trend that divalent sulfur functionalities are more reactive than trivalent sp -hybridized nitrogen compounds P. 

Elimination of sulfinic acid from ketosulfones was also a key step in an expedient synthesis of a,0-unsaturated ketones via the Michael adducts of sulfonyl carbanions to nitroalkenes. Conversion of the resulting nitronates into ketones was most conveniently realized by ozonolysis. DBU-promoted elimination of sulfinic add completed the process. Overall yields range from 71 to 88% for the examples reported [425]. 

The possibility of reducing sulfones to sulfinic acids was used for the synthesis of substituted 4-oxoazetidines 627 628) ... 

Thiazolyl sulfamic acids, rearrangement of sulfonic acid, 70 rearrangement to sulfonic acid, 75 by sulfonation, 75 2-Thiazolyl sulfenyl chloride, transformation to, thiazolyl disulfides. 412 2-Thiazolyl sulfide, in hydrocarbon synthesis, 406 oxidation of, with m-chloroperbenzoic acid, 415 with CrOj, 415 with Hj02,405,415 with KMn04,415 physical properties, infrared, 405 NMR, 404 pKa, 404 ultraviolet, 404 preparation of, from 2-halothiazoles and 5-Thiazolyl sulfides, bis-5-thiazolyl sulfide, oxidation of, 415 general, 418 5-(2-hydroxythiazolyl)phenyl sulfide case, 418 physical properties, 418 preparation of, 417-418 table of compounds, 493-496 uses of. 442 2-Thiazolyl sulfinic acid, decomposition of, 413 preparation of, from 2-acetamidothiazole sulfonyl chloride, 413 from A-4-thiazoline-2-thione and H, 0, 393,413 table of compounds, 472-473 5-Thiazolyl sulfinic add, preparation of,... 

So far, this method has been employed for the synthesis of (1) (Z)-(jS-sulfonylvinyl)-iodonium tetrafluoroborates from alkynyliodonium tetrafluoroborates with sulfinic acids in methanol (equation 46)32,84, (2) (Z )-(/ -azidovinyl)iodonium tetrafluoroborates from alkynyliodonium tetrafluoroborates with Me3SiN3, H20 (i.e. HN3) in dichloromethane (equation 110)102 and (3) (Z )-/ -bromo- and (jS-chlorovinyl)iodonium halides from alkynyliodonium tetrafluoroborates with lithium halides in acetic acid or with HX in methanol (equation 111 and 112)103. 

The chlorosulfite method, which is claimed to be indicated for the synthesis of alkanesulfmates, works only in the case of methanesulfinate. The levels of control of diastereomeric excess with arylzinc and any arylmetal were in general very low. Additionally, reaction of chlorosulfite esters with alcohols and amines produced sulfinic acid derivatives in good yield but with low selectivity (< 2 1). 

Figure 14.7. Pathways for the synthesis of taurine from cysteine. Cysteine sulfinate decarboxylase, EC 4.1.1.29 cysteic acid decarboxylase, EC 4.1.1.29 (glutamate decarboxylase, EC 4.1.1.15) cysteine oxidase, EC 1.13.11.20 cysteamine oxygenase, EC 1.13.11.19 and hypotaurine oxidase, EC 1.8.1.3. Relative molecular masses (Mr) cysteine, 121.2 cysteamine, 77.2 cysteine sulfinic acid, 153.2 cysteic acid, 169.2 hypotaurine, 109.1 and taurine, 125.1.

Taurine is a dietary essential in the cat, which is an obligate carnivore with a limited capacity for taurine synthesis from cysteine. On a taurine-free diet, neither supplementary methionine nor cysteine will maintain normal plasma concentrations of taurine, because cats have an alternative pathway of cysteine metabolism reaction with mevalonic acid to yield felinine (3-hydroxy-1,1-dimethylpropyl-cysteine), which is excreted in the urine. The activity of cysteine sulfinic acid decarboxylase in cat liver is very low. 

Until recently, dihydrothiazine oxides had not found much use in synthesis. Recently, Weinreb and coworkers have exploited some of the known reactions of these adducts, along with some new transformations, in stereoselective preparation of some complex nitrogen-containing molecules. One useful transformation of these adducts is the hydrolysis/retro-ene elimination of sulfur dioxide shown in equation (53). Thus dihydrothiazine oxide (120), prepared from ( , )-tetramethylbutadiene, underwent hydrolysis to allylic sulfinic acid (121) which suffered a retro-ene reaction via the chair-like conformation... 

---