Dimethyl sulphate, hydrolysis

The hydrolysis of dimethyl sulphate also provides a source of sulphate ion, and the reaction has been used for the precipitation of barium, strontium, and calcium as well as lead ... 

This reagent has proved especially important in the study of the constitution of the sugars, and of cellulose. A series of methyl-celluloses has been obtained, and by the study of their hydrolysis, or decomposition in a vacuum, some light has been thrown on the structure of the cellulose molecule. (J. S. C. I., 41, 362 R.) In the laboratory dimethyl sulphate is much employed in the methylation of phenols and naphthols. Diethyl sulphate is not so suitable for such alkylations as its lower homo-logue. 

The synthesis of the partially methylated glucoside, methyl 2,3-di-O-methyl-a-D-glucopyranoside (34) (Expt 5.121) also utilises the 4,6-O-benzylidene derivative (27), which is first converted into the 2,3-di-O-methyl derivative (33) by reaction with dimethyl sulphate in the presence of sodium hydroxide. Selective removal of the acetal grouping is achieved by mild acid hydrolysis the methyl ether groups are stable under both acidic and basic conditions. 

The first synthesis of 2,3,4-trimethyl-D-galactose, which had previously been isolated from the hydrolysis products of methylated galac-tosans, was achieved by McCreath and F. Smith.20 1,6-Anhydro-D-galactopyranose, treated with dimethyl sulphate and alkali, underwent easy methylation and the resulting crystalline 2,3,4-trimethyl-l,6-anhydro-D-galactopyranose was conveniently hydrolyzed to the free sugar hydrate. 

Recently, a new and efficient synthesis of cyprodime from naltrexone (2) has been reported [73], Firstly, the tetrazolyl ether (27) was formed by reaction of naltrexone with 5-chloro-l-phenyl-1 Ff-tetrazole [74], Catalytic hydrogenation afforded 3-deoxynaltrexone (28) which was methylated with dimethyl sulphate to give the enol ether (29). Acid hydrolysis gave the known morphinanone (30) [75] which was treated with activated zinc and ammonium chloride to yield the phenol (31). 4-O-Methylation with phenyltri-methylammonium chloride afforded cyprodime (23, Scheme 3.4) [75],... 

That is, unlike the sulphuric esters, methyl sulphuric acid and dimethyl sulphate, it does not split off its alkyl group on hydrolysis, but oifly the chlorine atom. 

The observed reactivity sequence for aliphatic sulphonates closely resembles that for the corresponding aliphatic sulphates ethylene sulphate, trimethylene sulphate and dimethyl sulphate (12 1 6)127 for which S—O bond fission (14%) was again only observed for the hydrolysis of a five-membered cyclic sulphate. The heats of hydrolysis have, however, been measured for aliphatic sulphate esters and the existence of considerable ring strain in the five-membered system is indicated by the fact that the heat of hydrolysis of ethylene sulphate exceeds that of dimethyl sulphate by 5-6kcalmol-121. 

Methylphenobarbital can also be prepared by the interaction of ethylphenyl malonie ester and dicyandiamide when it results into the formation of 5-ethyl-5-phenyl-3-cyano barbituric acid, which on methylation with dimethyl sulphate yields 5-ethyl-5-phenyl-3-cyano-1-methyl barbituric acid. This on acid hydrolysis converts the cyano moiety at position 3 into a free COOH group which on decarboxylation finally gives methylphenobarbital. 

Acetone cyanohydrin is obtained from the interaction of acetone and hydrocyanic acid, which on subsequent hydrolysis followed by esterification with ethanol yields ethyldimethylglycolate. This is condensed with urea in the presence of sodium ethoxide to yield 5, 5-dimethyl-oxazolidinedione-2, 4-dione. Trimethadione is finally obtained by treating the resulting product with dimethyl sulphate in the presence of sodium hydroxide. 

N-(prop-2-ynyl)amines to l-aminopropa-l,2-dienes followed by acid hydrolysis (e.g. Scheme 50). Treatment of the lithiated intermediate with dimethyl sulphate instead of methanol gives the 3-methylaldehyde, and deuterium atoms can also be introduced specifically. 

Bacillus polymyxa mannan. The purified mannan [a]n -f-82 was electro-phoretically homogeneous but appeared to contain some 13 % bound protein or peptide. Methylation with dimethyl sulphate/NaOH and later silver oxide/methyl iodide in dimethylformamide afforded a methyl ether [a]n +92 in chloroform and containing OCH3, 38.2%. Formic acid hydrolysis followed by further treatment with o.i N hydrochloric acid gave a mixture of ethers characterised as 2,3,4,6-tetra-O-methyl-D-mannose (identified by oxidation to the lactone and isolation of a crystalline phenylhydrazide),... 

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