Methanethiol reactions

When two equivalents of methanethiol were added to the reaction mixture, 12% of the rm-butyl ether along with 34% of l-methylene-2-(methylsulfanyl)cyclopropane(3) were obtained. - Product 3 could be obtained in 51% yield by using 4 equivalents of methanethiol. Reaction of 2-bromo-l-chloro-l-methylcyclopropane (1, X = Br) with potassium tert-butoxide in tetrahydrofuran, and with potassium tert-butoxide plus methanethiol in dimethyl sulfoxide, likewise gave the tert-butyl and sulfanylmethyl ethers in 30 and 47% yield, respectively. 

Minor amounts of methane and hydrogen sulphide in the methanethiol reaction and of ethane, ethylene and hydrogen sulphide in the ethanethiol reaction were also formed. The authors propose that these products are not formed in a primary process, but they derive from reaction of the thiol with a disulphide molecule which has not yet transferred the excess of energy which it contains at the act of formation (Scheme 10). 

Thermal Stability. Dimethyl sulfoxide decomposes slowly at 189°C to a mixture of products that includes methanethiol, formaldehyde, water, bis(methylthio)methane, dimethyl disulfide, dimethyl sulfone, and dimethyl sulfide. The decomposition is accelerated by acids, glycols, or amides (30). This product mixture suggests a sequence in which DMSO initially undergoes a Pummerer reaction to give (methylthio)methano1, which is labile and reacts according to equations 1—3. Disproportionation (eq. 4) also occurs to a small extent ... 

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. 

The main by-product of this type of reaction is the sulfide. For the synthesis of methanethiol (eq. 6), the main by-product is 2-thiapropane, CH SCH. This material has a variety of uses and is further processed. 

Decomposition of Thiols. Thiols decompose by two principal paths (i43— i45). These are the carbon—sulfur bond homolysis and the unimolecular decomposition to alkene and hydrogen sulfide. For methanethiol, the only available route is homolysis, as in reaction 29. For ethanethiol, the favored route is formation of ethylene and hydrogen sulfide via the unimolecular process, as in reaction 30. 

The addition of nucleophiles to double and triple bond systems is often a convenient way of effecting an intramolecular ring closure. Addition to cyano groups has received considerable attention, as in addition to ring formation it provides a convenient method for the introduction of an amino group. Reaction of methyl Af-cyanodithiocarbimidate with Af-methylaminoacetonitrile resulted in displacement of methanethiol and formation of (314). Sodium ethoxide treatment in DMF converted (314) into a 4-amino-5-cyanoimidazole... 

Although the nitro group plays a crucial role in most of these SrnI reactions, reactions of this type have synthetic application beyond the area of nitro compounds. The nitromethyl groups can be converted to other functional groups, including aldehydes and carboxylic acids.Nitro groups at tertiary positions can be reductively removed by reaction with the methanethiol anion.This reaction also appears to be of the electron-transfer type, with the methanethiolate anion acting as the electron donor ... 

In the early work, benzene formed the basis of a variety of multi-armed structures. Analogs bearing from 2—6 arms were prepared and compared for cation binding ability. The only indication of mode of synthesis for the hexa-substituted benzene derivative is that it was obtained on reaction of benzene-hexakis(methanethiol) and l-bromo-3,6,9-trioxatridecane . The reaction is illustrated in Eq. (7.6), below, devoid of reaction conditions and yields which were not specified. 

Ben2yloxyindolyl-3)-Q -acetvlamino-Q -methylthiopropionic acid methanethiol ester (449 mg) was added to 10 ml of ethanol and further 1 ml of triethylamine was added to the mixture. Then, the reaction mixture was refluxed for 17 hours, after condensation under reduced pressure and subsequent separation of the residue by column chromatography (silica gel, ethyl acetate), 353 mg of methyl -(5-benzyloxyindolyl-3)-Q -acetylamino-Q -methylthio-propionate was obtained as colorless glasslike substance in the yield of 81.5%. Recrystallization of the substance from methanol water afforded 287 mg of crystals. 

Thiophenolate complexes have been discussed, however, a considerable amount of alkylthiolate zinc chemistry is also known. The zinc alkylthiolate complexes with methanethiolate, ethanethiolate, and /. so-propylthiolate have been synthesized and characterized as precursors for ZnS formation. Thermolysis studies demonstrated the formation of ZnS and release of dimethylsulfide. Reactivity was similar with only the rm-propyl derivative showing much slower reaction.523 The polyzincate Zni0S4(SEt)i2L4 is a well-characterized neutral zinc sulfur compound.524... 

Oren, Z. et al., Israeli PatentIL 89641, 1995 Chem. Abs., 1996, 124, 260401g It is claimed that a prior method of manufacture from acetonitrile, methanethiol and hydroxylamine hydrochloride gave uncontrolled reaction and explosion. A safer preparation starting from acetaldoxime is claimed. 

Sulfonium salt 103a also underwent ring-opening reactions with nucleophiles, such as NaBH4, sodium azide, and sodium methanethiolate, to afford trithiocins 107 (see Equation (30) and Table 18) <1996BCJ2349> and <1998BCJ1187>. 

The reactions of glutathione and cysteine esters have been modeled by the reaction of methanethiol with A-formyloxy-A-methoxyformamide 40 at the BP/ DN //6-31G level.45 The transition state (Fig. 24) possesses similar characteristics... 

The submitter used methanethiol (b.p. 8°) obtained from Matheson Gas Products. The weight of the methanethiol distilled from the lecture bottle into the reaction flask was measured by difference. The pungent odor of this mercaptan is minimized by slow distillation of the reagent into the flask and by the use of a well-ventilated hood. The checkers used methanethiol (b.p. 8°, d 0.8948) obtained from Toyo Chemical Industries Co. (Japan) and changed the above procedure as follows methanethiol distilled from the lecture bottle was first trapped in an ice-cooled graduated flask equipped with a gas inlet and a dry ice reflux condenser, then 56 ml. of the liquid was redistilled into the reaction mixture. 

By far most of the reports on addition reactions of hetero-nucleophiles to activated dienes deal with sulfur-nucleophiles17,48,80,120-137, in particular in the synthesis of 7/3-sulfur-substituted steroids which, like their carbon-substituted counterparts (Section n.A), are of interest because of their ability to inhibit the biosynthesis of estrogens80,129-137. Early investigations17,120-122 concentrated on simple acyclic Michael acceptors like methyl sorbate and 2,4-pentadienenitrile. Bravo and coworkers120 observed the formation of a 3 1 mixture of the 1,6- and 1,4-adduct in the reaction of methyl sorbate with methanethiol in basic medium (equation 39). In contrast to this, 2,4-pentadienenitrile adds various thiols regioselectively at C-5, i.e. in a 1,6-fashion (equation 40)17,121,122, and the same is true for reactions of this substrate with hydrogen sulfide (equation 41), sodium bisulfite and ethyl thioglycolate17. 

Grosjean, D. Atmospheric reactions of ortho cresol gas phase and aerosol products, Atmos. Environ., 19(8) 1641-1652,1984. Grosjean, D. Photooxidation of methyl sulfide, ethyl sulfide, and methanethiol, Environ. Sci. Technol, 18(6) 460-468,1984a. Grosjean, D. Atmospheric reactions of styrenes and peroxybenzoyl nitrate, ScL Total Environ., 50 41-59, 1985. 

The reaction of p-D-ribopyranose tetraacetate (63) with methanethiol and zinc chloride gave 32), after deacetylation, methyl 1-thio-p-D-ribo-pyranoside (64), methyl 1,5-dithio-p-D-ribopyranoside (72, R=H), 4-S-methyl-4-thio-L-lyxose dimethyl dithioacetal (77, R=H), and a small... 

This enzyme [EC 4.2.99.10], also referred to as O-acetyl-homoserine sulfhydrylase, catalyzes the reaction of O-acetylhomoserine with methanethiol to generate methionine and acetate. The enzyme can also act on other thiols or H2S, producing homocysteine or thioethers. The enzyme isolated from baker s yeast will also catalyze the reaction exhibited by O-acetylserine (thiol)-lyase [EC 4.2.99.8], albeit more slowly. 

This pyridoxal-phosphate-dependent enzyme [EC 4.2.99.9], also known as cystathionine y-synthase, catalyzes the reaction of O-succinyl-L-homoserine with L-cysteine to produce cystathionine and succinate. The enzyme can also use hydrogen sulfide and methanethiol as substrates, producing homocysteine and methionine, respectively. In the absence of a thiol, the enzyme can also catalyze a /3,y-elimination reaction to form 2-oxobu-tanoate, succinate, and ammonia. 

The Sjv2 reaction has also been investigated theoretically at HF/6-31G and BPDN // 6-31G density functional levels using the model compounds methanethiol and A-formyloxy-A-methoxyformamide (91). As was reported for the ammonia reaction (Section... 

The key step in this synthesis is an intramolecular nucleophilic attack on the electron-rich indole nucleus by the carbocation derived from the p-keto sulfoxide in the presence of acid. Finally, the intermediate tetrahydrocarbazole aromatizes by elimination of methanethiol under the conditions of the reaction to produce the hydroxycarbazole (511) (Scheme 5.12). 

Hydrogen sulfide also reacts with many types of organic substances. Reaction with methanol at high temperatures in the presence of an acidic catalyst yields methanethiol and dimethylsulfide ... 

In the presence of a catalytic amount of methanethiolate-bridged diruthenium complex (la abbreviated as met-DIRUX), reactions of propargylic alcohols (2) with a variety of heteroatom-centered nucleophiles such as alcohols, thiols, amines, amides, and diphenylphosphine oxide gave the corresponding propargylic substituted... 

Examples of nucleophilic attack at the saturated 2-carbon of dihydro-l,4-thiazines, which may be assisted by the neighboring sulfur atom, are shown below. The nucleophiles include water, which was used in the acid-catalyzed hydrolysis of the ketal in 236 (Equation 21) <1982S424>, methanol in the conversion of 214 into a monothioacetal (Equation 22) <1982JHC131>, ethanol and dimethylaniline, which both reacted with 237 (Scheme 29) <1982TL4963>, and triethyl phosphite that was used to convert 238 into the phosphonate 239 required for Wadsworth-Emmons reaction (Equation 23) <2004BML1477>. Compound 240 reacted with both methanol and methanethiol (Equation 24) <1990JME1898>. 

Another cycloaddition to an a,(3-unsaturated compound involves the reaction of nitrile oxides with 3-methoxy- or 3-methylthio-1 -phenyl-2-propene-1 -one (Scheme 6.18) (133,134). The isoxazoles that are isolated are considered to arise from the respective intermediate isoxazolines by subsequent elimination of methanol or methanethiol. The regioselectivity observed was attributed to the presence of substituents with strong electron-donating ability, and this was accommodated in terms of the FMO theory (133,134). 

The reaction of 6-aminouracils 157 with dimethyl Ai-cyanodithioimidocarbonate, shown in Scheme 27, gave the intermediates 158 which on coupling to phenyldiazonium salt, followed by elimination of methanethiol, gave the 5,7-disubstituted-2-phenylpyrimido[4,5- ]-l,2,4-triazines 159 (Ar = Ph) in the isolated yields shown in Table 10 (entries... 

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