Methanethiolate ion

If 34 is, in turn, treated by carbon disulfide in basic medium, a dianion (35) is formed, which can lose a methanethiolate ion if conformation 36 is possible, giving the monoanion (37).55 57... 

Nucleophilic displacement of halogen by thiophenol occurs in 1-substituted 2-halogenobenzimidazoles and in l,3-diakyl-2-chlorobenzimidazolium tetrafluoroborates. The reactions of 4-haloimidazolium salts with sulfide or methanethiolate ions are accompanied by some replacement of halogen, but reduction and ring cleavage to give N- methyl-thioamides can also take place. 

The substitution of perfluoroalkyl iodide by methanethiolate ion (72) is not a straightforward 8 2 process. The mechanism has been established as shown. 

The rate and activation parameters have been determined for the reaction of potassium methanethiolate with various 2-fluoro- and bromo-pyridines. Although an ortAo-methyl group did not activate the 2- position in 2-bromo- or 2-fluoro-pyridine towards attack by the methanethiolate ion, deactivation of the ortho rather than the para position was observed. At 110°C for the bromo-compounds Ao-Me Xp-Me = 3-9, while Ao-Br A -Br = 2-2. The results have been compared with those obtained using methoxide and benzenethiolate anions in methanol. The relative rates observed in HMPA are the same as those in methanoP . Thio-phenol reacts faster than its anion with a bromopyridine, in methanol, due to a rapid acid-base pre-equilibrium in which the pyridine is protonated. An o-MeO substituent accelerates the replacement of Br, and a small increase is also noted on going from MeOH to DMSO as solvenpii. 

Dmowski W, Haas A (1985) Chimia 39 185 (b) Dmowski W, Haas A (1987) Trifluoro-methanethiolate ion. Part 2. Nucleophilic substitution in pentafluoropyridine. Synthesis and characteristics of trifluoromethylthio and trifluoromethylsulphonyl derivatives. J Chem Soc Perkin Trans 1 2119-2124. doi 10.1039/P19870002119 (c) Dmowski W, Haas A (1988) Tiifluoromethanethiolate ion. Part 3. Reactions with tetrafluoropyridazine and tetrafluoropy-limidine. J Chem Soc Perkin Trans 1 1179-1181. doi 10.1039/P19880001179... 

In contrast to the case of uridine derivatives noted above, attempts to carry out a Corey-Winter fragmentation of N, 5 - protected cytidine 2 ,3 -thionocarbonates caused isomerisation to 2 -deoxy-2 -thiocytldine-2, 3 -carbonates (69). 121 The 3 -thiomethyl-, methylsulphinyl-, and methylsulphonyl derivatives of 3 -deoxythymidine have been prepared by treatment of the 5 -0-trltyl derivative of (63) with methanethiolate ion, followed by oxidation at sulphur and deprotection as appropriate. 122... 

Ethyl methyl sulfide 1,1-DimethylethyI 2-Methyltliioethanol Methanethiolate ion... 

When DMSO is mixed with concentrated hydrochloric acid, protonated DMSO is in equiUbtium with the chlorodimethylsiilfonium ion. Pummerer reactions and subsequent reaction of the initial products give a complex mixture of products including formaldehyde, bis(methylthio)methane, methanethiol, dimethyl disulfide, dimethyl sulfide, and others. 

Similarly, proton induced elimination of neutral molecules has also been utilized to generate 1,3-diselenolylium and 1,3-thiaselenolylium ions. As shown in Scheme 8, protonation of 2-methylthio- or 2-methylseleno-l,3-dichalcogenoles with fluoroboric acid results in loss of methanethiol or methaneselenol and in formation of the corresponding 1,3-dichalcogenolylium ions (80H(14)27l, 75TL1259). 

Tetra-O-acetyl-5-thio-a-D-xylopyranose can be transformed into the crystalline a-D-glycosyl bromide (213) by the action of hydrogen bromide in acetic acid. Compound 213 undergoes deacetylation with sodium methoxide to form methyl 5-thio-j8-I>-xylopyranoside (218). In the presence of sodium methoxide and methanethiol, 213 forms methyl l,5-dithio-j8-D-xylopyranoside (219). Compound 219 is so sensitive toward acidic methanol that it is transformed into methyl 5-thio-j3-D-xylopyranoside (218) on neutralization of the basic reaction mixture with an acid ion-exchange resin. 

Kinetics have been determined for the displacement of the methylthio group from 2-methylthiopyrazine by methoxide ion. At 129.9° the rate coefficient was 2.83 X 10" 1/mol sec, energy of activation 24.6kcal/mol, and logyl 10.76 (1080). The reaction was bimolecular but the methoxide ion concentration remained constant throughout the reaction owing to its regeneration from the oxidation of the methanethiol produced (1080). 

Chloro- or 3-bromo-l,2-dithiolium ions react with hydrogen sulfide or methanethiolate anions giving l,2-dithiole-3-thiones or 3-methylthio-l,2-dithiolium ions, respectively (Scheme 16). °... 

Desulfation of organic sulfate esters with the release of sulfate ion is identified with enzymes such as glycosulfatase in the red algae, Porphyra umbilicus (Rees, 1961). However organic esters may be reduced to liberate methanethiol or dimethyl sulfide. Young and Maw (1958) reported that the fungus, Schizophyllum commune, synthesises dimethyl sulfide and methyl sulfide by the following successive reduction and methylation reactions ... 

---