Acetic mercapto

The prefix thioxo- is used for naming =S in a thioketone. Sulfur analogs of acetals are named as alkylthio- or arylthio-. For example, CH3CH(SCH3)OCH3 is l-methoxy-l-(methylthio)ethane. Prefix forms for -carbothioic acids are hydroxy(thiocarbonyl)- when referring to the O-substituted acid and mercapto(carbonyl)- for the S-substituted acid. 

The use of an acidic solution of p-anisaldehyde in ethanol to detect aldehyde functionalities on polystyrene polymer supports has been reported (beads are treated with a freshly made solution of p-anisaldehyde (2.55 mL), ethanol (88 mL), sulfuric acid (9 mL), acetic acid (1 mL) and heated at 110°C for 4 min). The colour of the beads depends on the percentage of CHO content such that at 0% of CHO groups, the beads are colourless, -50% CHO content, the beads appear red and at 98% CHO the beads appear burgundy [Vdzquez and Albericio Tetrahedron Lett 42 6691 200]]. A different approach utilises 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole (Purpald) as the visualizing agent for CHO groups. Resins containing aldehyde functionalities turn dark brown to purple after a 5 min reaction followed by a 10 minute air oxidation [Coumoyer et al. J Comb Chem 4 120 2002]. 

Alkylthio, arylthio, and thioxo. The thioxo group in pyrimidine-2,4-dithione can be displaced by amines, ammonia, and amine acetates, and this amination is specific for the 4-position in pyrimidines and quinazolines. 2-Substitution fails even when a 5-substituent (cf. 134) sterically prevents reaction of a secondary amine at the 4-position. Acid hydrolysis of pyrimidine-2,4-dithione is selective at the 4-position. 2-Amination of 2-thiobarbituric acid and its /S-methyl derivative has been reported. Under more basic conditions, anionization of thioxo compounds decreases the reactivity 2-thiouracil is less reactive toward hot alkali than is the iS-methyl analog. Hydrazine has been reported to replace (95°, 6 hr, 65% 3deld) the 2-thioxo group in 5-hexyl-6-methyl-2-thiouracil. Ortho and para mercapto- or thio- azines are actually in the thione form. ... 

Substituents in the 6-position (cf. 267) show appreciable reactivity. 6-Bromo-as-triazine-3,5(2j, 4j )-dione (316) undergoes 6-substitution with secondary amines or hydrazine, with mercaptide anions or thiourea (78°, 16 hr), with molten ammonium acetate (170°, 24 hr, 53% yield), and with chloride ion during phosphorous oxychloride treatment to form 3,5,6-trichloro-as-triazine. The latter was characterized as the chloro analog of 316 by treatment with methanol (20°, heat evolution) and hydrolysis (neutral or acid) to the dioxo compound. The mercapto substituent in 6-mercapto-as-triazine-3,5(2iI,4if)-dione is displaced by secondary... 

Treatment of 3,4-dinitrofurazan with potassium thiocyanate in acetic acid at 10-20°C led to the corresponding thiocyanate 214 in 83% yield along with a small amount of 3-mercapto-4-nitrofurazan, whereas at 70-75°C the precursor was converted into a mixture of the disulfide 215 (38%) and tricycle 216 (27%). Thioether 217 was prepared in 78% yield by reaction of 3,4-dinitrofurazan and sodium sulfide (95MC25) (Scheme 145). 

According to REM, hydrazine hydrate Is reacted with 2 mols of ammonium thiocyanate to produce 1,2-bislthlocarbamoyl) hydrazine which by loss of ammonia and rearrangement produces 5-amino-2-mercapto-1,3,4-thiadiazole. That compound is acetyied with acetic anhydride. 

Then, as described in U.S. Patent 2,55416, the 2-acetylamido-5-mercapto-1,3,4-thiadiazole is converted to the sulfonyl chloride by passing chlorine gas into a cooled (5°-10°C) solution in 33% acetic acid (66 parts to 4 parts of mercapto compound) used as a reaction medium. Chlorine treatment is continued for two hours. The crude product can be dried and purified by recrystallization from ethylene chloride. The pure compound is a white crystalline solid, MP l94°C,with decomposition, when heated rapidly. The crude damp sulfonyl chloride is converted to the sulfonamide by addition to a large excess of liquid ammonia. The product is purified by recrystallization from water. The pure compound is a white, crystalline solid, MP 259°C, with decomposition. The yield of sulfonamide was 85% of theory based on mercapto compound. 

Finally,Captopril is produced. Thethioester (0.85g) isdissolved in5.5N methanolicammonia and the solution is kept at room temperature for 2 hours. The solvent is removed in vacuo and the residue Is dissolved in water, applied to an ion exchange column on the H cycle (Dowex 50, analytical grade) and eluted with water. The fractions that give positive thiol reaction are pooled and freeze dried. The residue Is crystallized from ethyl acetate-hexane, yield 0.3 g. The 1 -(3-mercapto-2-D-methylpropanoyl)-L-proline has a melting point of 103°C to 104°C. 

N 24.12% brick red solid mp, decomps when heated over 300°. Insol in w and the usual organic solvents as well as weak acids and alkalies. Comm prepn (Ref 3) is from thiocyanic acid and/or thiocyanates either by anodic oxidation or by interaction with hydrogen peroxide or halogens. The yield is impure because it contains both H and O. The S content varies between 45 and 55%. Lab prepn of the pure polymer is by reacting the Na salt of 5-chlor-3-mercapto 1,2,4-thiodiazols with either acet, ethanol or w (Refs 1 2)... 

The synthesis of 2-substituted pyrimidines from 1,3-dicarbonyl compounds and urea derivatives was first described by Evans2 and was later improved by Hunt, McOmie, and Sayer3 for the preparation of 2-mercapto-4,6-dimethylpyrimidine. Burness4 employed 3-ketobutyraldehyde acetal in this procedure to give 2-mercapto-4-methylpyrimidine. 2-Mercaptopyrimidine has been prepared from 1,1,3,3-tetraethoxypropane and thiourea by variations of this basic method 3 6 6 as well as by the reaction of 2-chloropyrimidine with thiourea 1 or sodium hydrosulfide.8... 

Heating of the acetic acid ethyl ester-substituted mercapto-substituted pyrimidine 214 in acetic acid and sulfuric acid led to cyclodehydration to give the tricyclic system 215 in moderate yield (Equation 57) <2005PS(180)1629>. 

Akiyama Y, Otsuka H, Nagasaki Y, Kato M, Kataoka K (2000) Selective synthesis of heterobifunctional poly(ethylene glycol) derivatives containing both mercapto and acetal terminals. Bioconjug Chem 11 947-950... 

Mercapto-l,2,4-thiadiazoles exist as an equilibrium of tautomers with the equilibrium favoring the thione tautomer. They are acidic with a pA a of around 5. A variety of methylating agents (e.g., diazomethane, dimethyl sulfate and methyl iodide) give S-methylated products and no N-methylation has been observed. They are readily oxidized to sulfoxides and sulfones with either z-chloroperbenzoic acid or hydrogen peroxide in acetic acid <1996CHEC-II(4)307>. There have been no new publications on S-linked substituents since the publication of CHEC-II(1996). 

A non-aqueous titration method was developed (25,26) for the determination of basic compounds with thio(-S-) and mercapto (-SH-) groups. The reaction of the S group with Hg (0Ac)2 in acetic acid makes this possible. Methimazole and other compounds were all titrated with HCIO in acetic acid using gentian violet as indicator. 

Compound 98 reacts with carbon disulfide in the presence of an alkali solution to give 3 -mercapto-l,2,4-triazolo[4, 5 l,5][l,2,4]triazolo[3,4-A]benzothiazole 247. Treatment of product 98 with urea at 200°C for 4h affords 3 -hydroxy-l,2,4-triazolo[4, 5 l,5]-l,2,4-triazolo[3,4-A benzothiazole 99 (Scheme 20). Finally, the addition of concentrated phosphoric acid in the presence of sodium nitrite to compound 98 produces 1,2,3,4-tetra-zolo[l, 5 l,5]-l,2,4-triazolo[3,4- ]benzothiazole 248, and refluxing substituted benzaldehydes in acetic acid provides an easy access to 3 -aryl-l,2,4-triazolo[4, 5 l,5]-l,2,4-triazolo[3,4-A benzothiazoles 249 (Scheme 20) (Table 50) <2005IJC(B)625>. 

The reaction of 2-mercapto-4-(2, 4 -dichlorophenyl)-5-cyanopyrimidin-6(l//)one 421 (obtained by stirring ethyl cyanoacetate and thiourea with 2,4-dichlorobenzaldehyde in sodium ethylate at room temperature, in 70% yield), with a solution of monochloroacetic acid and />-cholorobenzaldehyde in glacial acetic acid, in the presence of sodium acetate, affords 2-[(/>-chlorophenyl)methylene]-6-cyano-7-(2, 4 -dichlorophenyl)thiazolo[3,2-tf]pyrimidin-3,5-dione 422. Finally, the reaction of compound 422 with hydrazine hydrate converts it into product 423 (Scheme 49) < 1996PS( 116)39>. 

Similarly, 3-(5-mercapto-l,2,4-triazol-3-yl)-7-methyl-l,4-dihydro-4-oxo-l,8-naphthyridines 432, after reaction with substituted benzaldehydes, chloroacetic acid in the presence of the mixture of acetic anhydride and acetic acid, gives the corresponding 3-(6-arylidene-5-oxo-5,6-dihydro-thiazolo[3,2- ]-l,2,4-triazol-2-yl)-7-methyl-l,4-dihydro4-oxo-1,8-naphthyridines 433 (Equation 92) <2002EJC323>. 

The same starting compound 270 was also subjected to ring closure by using other reagents <2003PS1143> reaction of 270 with acetic anhydride afforded the methyl-substituted 272, whereas reaction with carbon disulfide yielded the 3-mercapto derivative 273. 

Several crown ethers that possess side chains with terminal mercapto groups enhance the rate of transesterification of amino-acid p-nitrophenyl esters. Matsui and Koga (1978) reported the reactions of a number of amino-acid p-nitrophenyl ester hydrobromides dissolved in mixtures of ethanol and dichloromethane (1 4) and buffered with acetic acid and pyridine (pH 4.60 in... 

When two or more mercaptans are simultaneously oxidized, a mixture of several disulfide products can be formed. Oxidation of mercapto-acetate and n-butyl mercaptan (BSH) yields three possible disulfides ASSA, ASSB, and BSSB. 

Instead of the amino group, position 4 of the imidazole ring was involved in the reaction of 5-amino-2-mercapto-1 -methylimidazole (226) and EMME when they were heated under nitrogen, giving 4-imidazolylmethylenemalo-nate (227) (78H241). The same product was obtained when the hydrochloride of imidazole (226) was reacted with N,N-dimethylaminomethylene-malonate in DMF or acetic acid. 

Ethylgermaniumformates, acetates, and mercapto acetate. J. Amer. chem. 

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