Methanethiol conditions

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. 

The conjugate addition of a thiol, methanethiol, to the a,(5-unsaturated aldehyde acrolein may be used in the synthesis of the amino acid methionine. Under basic conditions, the nucleophile will be the thiolate anion, and 1,4-addition leads to the thia-aldehyde. Methionine may then be obtained via... 

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). 

The stability of substituted 1,2-dithianes toward ring-opening polymerization was tested by heating the disulfides with a catalytic amount of sodium methanethiolate <1989T91> none of the 1,2-dithianes were stable with respect to polymerization under these conditions. The thermal polymerization of 1,2-dithiane was also studied in detail <2005POJ512, 2004MM3143>. 

Loss of methanethiol from 132 following nucleophilic attack by a ring nitrogen atom under basic conditions, or thermally, afforded the s-triazolo[4,3-6]-s-triazole (133).135 In a recently reported reaction,136 methylation of the thioamide group in 134 resulted in cyclodeamination to give the quaternary salt 135 with loss of 2,6-dichloroaniline, rather than loss of methanethiol as in 132 - 133. 

Fluoro-l, 3-benzothiazoIe reacts with sodium methanethiolate to give 2-(mclhylsulfanyl)-1,3-benzothiazole under very gentle conditions,17 as given for 4-(aminosuIfonyl)-7-fluoro-2,l, 3-benzoxadiazole (vide supra). 

Under similar conditions, i.e. in dimethylformamide for three hours at 110 C, 6-fluoro-5/f-thia-zolo[2,3-6]quinazolin-5-one reacts with potassium methanethiolate, yielding 6-(methylsul-fanyl)-5//-thiazolo[2,3-6]quinazolin-5-onc (73% mp 186-189 C).24... 

Exercise 29-20 What conditions would you choose for producing the highest possible yield of (phenylmethylthio)phenylethane by radical-induced addition of phenyl-methanethiol to ethenylbenzene What structure would you expect the product to have Explain. 

Two mechanisms (i.e. direct hydrolysis and alternatively a path via an unstable acyl phosphate intermediate) are involved in the hydrolysis in phosphate buffer of N-arylsulfonyl / -lactams such as (130).107 The acyl phosphate intermediate can be trapped with hydrazine. The alkaline hydrolysis of some torsionally distorted lactams, i.e. the bridged benz[rfe]isoquinolin-l-ones (131), in 70% (v/v) DMSO-water has been compared under the same conditions with the hydrolysis of AvA-dimethyl-1 -naphthamide (132). The relative rates of reaction and activation parameters indicate the effect of torsional distortion.108 The reaction of the tricyclic azetidinones (133) with trifluoroacetic acid gives the bicyclic thioesters (135). The mechanism may involve acid-catalysed elimination of methanethiol to give an azetinone intermediate (134) which, after nucleophilic attack of the thiol, is converted into (135).109... 

This important flavor compound was identified in the head-space volatiles of beef broth by Brinkman, et al. (43) and although it has the odor of fresh onions, it is believed to contribute to the flavor of meat. This compound can be formed quite easily from Strecker degradation products. Schutte and Koenders (49) concluded that the most probable precursors for its formation were etha-nal, methanethiol and hydrogen sulfide. As shown in Figure 5, these immediate precursors are generated from alanine, methionine and cysteine in the presence of a Strecker degradation dicarbonyl compound such as pyruvaldehyde. These same precursors could also interact under similar conditions to give dimethyl disulfide and 3,5-dimethyl-l,2,4-trithiolane previously discussed. 

Reaction between 74 and alkyl / -ketoacetates or acetylacetone under the same conditions, however, furnishes cyclic 1,1-enediamines 77 with loss of one acetyl group39. The evidence available indicates the involvement of a consecutive reaction between the initially formed 1,1-enediamines 75 and the methanethiol released at the condensation step97. The methanethiol attacks the more reactive carbonyl group of the enediamine 75 to form the intermediate 76, which undergoes elimination to give the deacetylation products 77 and methyl thioacetate (78) (Scheme 6). 75 can survive in this reaction... 

Treatment of l,l-dichloro-la,9b-dihydrocyclopropa[/]phenanthfene with an excess of potassium tert-butoxide and methanethiol in dimethyl sulfoxide gave 1 a,9b-bis(methylsulfanyl)-l a,9b-dihydrocyclopropa[/]phenanthrene (3) in greater than 80% yield.The reaction conceivably involves cyclopropene intermediates 1 and 2 (cf ref 725), which are both trapped by mercaptide. This mechanism is supported by the fact that cnr/o-l-chloro-la-methylsulfanyl-la,9b-dihydrocyclopropa[/]phenanthrene (4) was isolated in good yield (68%) when the dichloride was reacted with 1 equivalent of potassium rert-butoxide and a deficit of methanethiol. l,l-Dichloro-la-methyl-la,9b-dihydrocyclopropa[/]phenanthrene reacts similarly under the same conditions to give cn[Pg.1409]

Quantitative studies on the enzymatic generation of methanethiol from methionine showed that methioninase obtained from Pseudomonas putida could be used for the development of flavors. Reactions carried out under anaerobic conditions yielded only methanethiol while aerobic conditions favored conversion of substantial amounts of methanethiol to dimethyl disulfide. Incorporation of free or fat-encapsulated methionine/methioninase systems into Cheddar cheeses resulted in the formation of volatile sulfur compounds, including carbon disulfide, and accelerated rates of development of aged Cheddar-like flavors. Methanethiol, when present alone, was observed not to cause the true, Cheddar-like flavor note in experimental cheeses. 

Since methloninase has potential applications in both aerobic and anaerobic food systems, a number of experiments were conducted to characterize and evaluate the performance of methloninase under a variety of these conditions. In these studies freeze-dried methloninase preparations (either 0.779 units/mg protein or 2.45 units/mg protein) were employed for generation of methanethiol, and selective flame photometric detection gas chromatography was use for quantifying methanethiol. The column was a 3 m x 4 mm id glass column packed with Carbopak BHT-100, and It was operated at 60°C isothermally for methanethiol analysis. When higher molecular weight sulfur compounds were measured also (e.g.,... 

Based on the concentration of methanethiol in the aged sample, conditions were established for the methioninase system which would approximate what might be encountered naturally, i.e., about 2 orders of magnitude greater than the target figure that was defined as the aged, full-flavored Cheddar cheese. 

Concentrations of methanethiol measured in headspace samples of the experimental cheeses are summarized in Table II for the analysis times of 1 day, 21 days and 4 months for each of the two ripening conditions employed. Notably, the cheese made with only encapsulated buffer did not contain methanethiol after 1 day at either temperature. However, the encapsulated methioninase system yielded significant amounts of methanethiol at 1 day, and continued to increase through 4 months. Generally, the final concentration of methanethiol in the encapsulated-buffer control... 

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