Demethyl disulfide

Methoxyl Groups Lignin is partially demethylated by the action of hydrosulfide ions forming methyl mercaptan which is convertible to dimethyl sulfide by reaction with another methoxyl group. In the presence of oxygen, methyl mercaptan can be oxidized further to dimethyl disulfide (Fig. 7-28). Because the hydroxide ions are less strong nucleophiles than hydrosulfide ions, only small amounts of methanol are formed. Methyl mercaptan and... 

Thiram and other dithiocarbamates are metabolic poisons. The acute effects of thiram are very similar to that of carbon disulfide, supporting the notion that the common metabolite of this compound is responsible for its toxic effects. The exact mechanism of toxicity is still unclear, however it has been postulated that the intracellular action of thiram involves metabolites of carbon disulfide, causing microsome injury and cytochrome P450 disruption, leading to increased heme-oxygenase activity. The intracellular mechanism of toxicity of thiram may include inhibition of monoamine oxidase, altered vitamin Bg and tryptophan metabolism, and cellular deprivation of zinc and copper. It induces accumulation of acetaldehyde in the bloodstream following ethanol or paraldehyde treatment. Thiram inhibits the in vitro conversion of dopamine to noradrenalin in cardiac and adrenal medulla cell preparations. It depresses some hepatic microsomal demethylation reactions, microsomal cytochrome P450 content and the synthesis of phospholipids. Thiram has also been shown to have moderate inhibitory action on decarboxylases and, in fish, on muscle acetylcholinesterases. 

Cleavage of ethers. Of many reagents tried for demethylation of 2,6-dimethoxy-4-methylbenzaldehyde, aluminum bromide proved to be the most satisfactory. A solution of the reagent in carbon disulfide was added to a stirred solution of the... 

Hepatic Effects. Male volunteers exposed for 6 hours to graded concentrations (10-80 ppm) of carbon disulfide showed inhibition of oxidative demethylation of orally administered amidopyrine (Mack et al. 1974). In another study, Vanhoome et al. (1992b) reported significantly increased liver size and y-glutamyltransferase (GGT) activity in 119 carbon disulfide-exposed workers compared to 79 controls. Workers had been exposed to 1-36 ppm for a mean of 42 years. However, since adequate exposure data were not presented, this study should be interpreted with caution. 

Chlorosulfonyl benzoates were synthesized from 2-aryldimethyloxazolines 17 (Scheme 5). Sequential treatment with n-butyllithium and dipropyl disulfide afforded sulfides 18. The oxazolines 18 were then hydrolyzed to the benzoic acids 19 under acidic conditions. Fisher esterification gave the esters 20, which were oxidized to the corresponding sulfonyl chlorides 21 using chlorine and aqueous acetic acid. When methoxy-substituted benzoic acids (19, X = OMe) were employed, further manipulations were performed prior to oxidation. For example, phenol (22) was prepared by demethylation with boron tribromide, subjected to esterification, and then alkylated by a variety of electrophiles to provide 23. As before, 23 was oxidized using chlorine and aqueous acetic acid. 

Preparation by demethylation of 2,4-dimethoxybenzophenone with aluminium bromide in refluxing benzene for 4 h (98%) [18], Also obtained by using aluminium chloride in refluxing carbon disulfide for 30 min (3%) [205], Preparation by Fries rearrangement of,... 

Preparation by partial demethylation of 2,4,5-trimethoxy-benzophenone with aluminium chloride in boiUng carbon disulfide for 1 h [761,762],... 

Also obtained by selective demethylation of 2,3 -dimelhoxybenzophenone in the presence of boron trichloride in methylene chloride at r.t. for 30 min [341,343]. Also obtained (poor yield) by reaction of 3-methoxybenzoyl chloride with ani-sole in the presence of aluminium chloride in refluxing carbon disulfide for 2 h [341]. 

Preparation by reaction of p-nitrobenzoyl chloride with m-methylanisole in the presence of aluminium chloride in carbon disulfide at 25° for 4 h, followed by demethylation of the keto ether so formed, that is to say 4-methoxy-2-methyl-4 -nitro-benzophenone (68%) [1110]. m.p. 194° [961], 191-192° [1110] Spectra (NA). 

Preparation by demethylation of 2-hydroxy-5-meth-oxy-4-methyl-3-nitroacetophenone with aluminium bromide in carbon disulfide at r.t. (96%) [2583]. 

Also obtained by demethylation of a mixture of 2-methoxy-4-pentylacetophe-none and 4-methoxy-2-pentylaceto-phenone (I) with boron tribromide in methylene chloride at 0° and separation of isomers by chromatography (21%). The mixture of anisoles (I) was obtained by reaction of acetic anhydride with 3-pentylanisole in the presence of aluminium chloride in refluxing carbon disulfide [3489],... 

Also obtained by Friedel-Crafts acetylation of 4-bromopyrogaUol trimethyl ether with acetyl chloride in the presence of aluminium chloride in carbon disulfide, then treatment of the compound obtained (partly demethylated) with dimethyl sulfate in the presence of sodium hydroxide [3833]. 

Also obtained by demethylation of 2-methoxy-6-methylpropiophenone with aluminium chloride in refluxing carbon disulfide for 6 h (14%) [7058]. 

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