scholarly journals Green chemistry metrics: a comparative evaluation of dimethyl carbonate, methyl iodide, dimethyl sulfate and methanol as methylating agents

2008 ◽  
Vol 10 (4) ◽  
pp. 457 ◽  
Author(s):  
Maurizio Selva ◽  
Alvise Perosa
Keyword(s):  
Green Chemistry ◽  
Methyl Iodide ◽  
Comparative Evaluation ◽  
Dimethyl Carbonate ◽  
Dimethyl Sulfate ◽  
Methylating Agents

Thiazoloisoquinolines. III. Structure and methylation of 2-hydroxythiazolo[4,5-c]- and -[5,4-c]isoquinolines

1968 ◽  
Vol 46 (5) ◽  
pp. 691-694 ◽  
Author(s):  
Catherine E. Hall ◽  
Alfred Taurins
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Methyl Iodide ◽  
Dimethyl Sulfate ◽  
The Other ◽  
Thiazole Ring ◽  
Spectral Evidence ◽  
Other Hand ◽  
Methylating Agents ◽  
Nuclear Magnetic

2-Hydroxythiazolo[4,5-c]isoquinoline (1) and 2-hydroxythiazolo[5,4-c]isoquinoline (2) were both found to exist predominantly in the lactam form (1b and 2b respectively) from infrared, nuclear magnetic resonance, and ultraviolet spectral evidence. Various methylating agents methylated compound 1 exclusively on the N-3 atom in the thiazole ring. Compound 2 on the other hand, gave a mixture of O-and N-3 methylated products with diazomethane and a mixture of N-1 and N-4 methylated products with either methyl iodide or dimethyl sulfate.

scholarly journals Single-Step Methylation of Chitosan Using Dimethyl Carbonate as a Green Methylating Agent

Molecules ◽  
2019 ◽  
Vol 24 (21) ◽  
pp. 3986 ◽  
Author(s):  
Ellen B. Hemming ◽  
Anthony F. Masters ◽  
Alvise Perosa ◽  
Maurizio Selva ◽  
Thomas Maschmeyer
Keyword(s):  
Ionic Liquid ◽  
Reaction Time ◽  
Nmr Spectroscopy ◽  
Methyl Iodide ◽  
1H Nmr ◽  
1H Nmr Spectroscopy ◽  
Dimethyl Carbonate ◽  
Dimethyl Sulfate ◽  
Single Step ◽  
Chitosan Derivative

N,N,N-Trimethyl chitosan (TMC) is one chitosan derivative that, because of its improved solubility, has been studied for industrial and pharmaceutic applications. Conventional methods for the synthesis of TMC involve the use of highly toxic and harmful reagents, such as methyl iodide and dimethyl sulfate (DMS). Although the methylation of dimethylated chitosan to TMC by dimethyl carbonate (DMC, a green and benign methylating agent) was reported recently, it involved a formaldehyde-based procedure. In this paper we report the single-step synthesis of TMC from chitosan using DMC in an ionic liquid. The TMC synthesised was characterised by 1H NMR spectroscopy and a functionally meaningful degree of quaternisation of 9% was demonstrated after a 12-h reaction time.

THE CHEMICAL STABILITY OF THE S-METHYL XANTHATES OF SOME SIMPLE ALCOHOLS

1956 ◽  
Vol 34 (9) ◽  
pp. 1302-1314 ◽  
Author(s):  
D. L. Vincent ◽  
C. B. Purves
Keyword(s):  
Hydrogen Peroxide ◽  
Methyl Ester ◽  
Methyl Iodide ◽  
Chemical Stability ◽  
Periodic Acid ◽  
High Yield ◽  
Methylating Agents ◽  
First Time ◽  
Oxygen Atoms

n-Octadecyl S-methyl xanthate, m.p. 38–39°, and n-hexadecyl S-methyl xanthate, m.p. 28–28.5°, were prepared for the first time, and were used to study the behavior of the S-methyl xanthate group toward reagents commonly used in research on carbohydrates. Although stable to some conditions of acetylation, hydrolysis, and methanolysis, the S-methyl xanthate group was destroyed by all methylating agents tried, with the exception of nitrosomethylurethane. The latter reagent converted a sodium xanthate salt in high yield to the S-methyl ester. Octadecyl and hexadecyl S-methyl xanthates when oxidized with hydrogen peroxide yielded crystalline substances of composition C20H40O4S2 and C18H36O4S2, respectively, whose structures were not determined. These substances each contained three additional oxygen atoms. Various attempts to estimate the S-methyl xanthate group by oxidation with bromine or periodic acid, or by reduction to methyl iodide, were unsuccessful.

C-Methylation Of Organic Substrates. A Comprehensive Overview. Part Iva. Methylating Agents Other Than Methane, Methanol, And Methyl Metals

2021 ◽  
Vol 01 ◽  
Author(s):  
Saad Moulay
Keyword(s):  
Transition Metal Complexes ◽  
Dimethyl Carbonate ◽  
Emission Tomography ◽  
Dimethyl Formamide ◽  
Organic Substrates ◽  
Comprehensive Overview ◽  
Methyl Halides ◽  
Aromatic Substrates ◽  
Positron Emission ◽  
Methylating Agents

: C-Methylation of organic substrates was accomplished with a number of methylating agents other than methane, methanol, and methyl metals. They include methyl halides (MeX, X = I, Br, Cl, F), methyl-containing halogenated reagents, methyl peroxides, dimethyl carbonate (DMC), dimethylsulfoxide (DMSO), N,N-dimethyl formamide (DMF), diazomethane, formate salts, trioxane, CO/H2, CO2/H2, and dimethyl ether (DME). Under particular conditions, some methyl-containing molecules such as polymethylbenzenes, methylhydrazine, tris(diethylamino)sulfonium difluorotrimethylsilicate, methyl tosylate, long-chain alkyl alcohols, and acetic acid unexpectedly C-methylated a variety of organic substrates. A few cases of C-methylation only were reported to occur in the absence of catalysts. Otherwise, transition metal complexes as catalysts in conjunction with specific ligands and bases were ubiquitously present in most C-methylation reactions. Of the reactions, Suzuki-Miyaura-type cross-coupling remained of paramount importance in making 11CH3-bearing positron emission tomography tracers (PETs), one of the best applications of such methylation. Methylation proceeded at C(aromatic)-X, C(sp3)-X C(sp2)-X, and C(sp)-X of substrates (X = H, halogen). Ortho-methylation was regioselectively observed with aromatic substrates when they bear moieties such as pyridyl, pyrimidyl, amide, and imine functionalities, which were accordingly coined ‘ortho-directing groups’.

ChemInform Abstract: Dimethyl Carbonate vs. Dimethyl Sulfate

ChemInform ◽  
1990 ◽  
Vol 21 (45) ◽  
Author(s):  
M. LISSEL ◽  
A. R. ROHANI-DEZFULI
Keyword(s):  
Dimethyl Carbonate ◽  
Dimethyl Sulfate
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