Methyl
p-toluenesulfonate is not as harmless as dimethylcarbonate but definitive less toxic than dimethylsulfate or methyl iodide. Depending on the chemical company selling it methyl
p-toluenesulfonate is either rated as irritating or 'may cause cancer'. Bees handling it should wear proper protecting clothes and handle this stuff with care.
As it can bee prepared OTC it offers an alternative to DMS and MeI but as far as TFSE told there is no working instruction or write-up in the Hive or at Rhodium's page.
Here are some practical applications (some are quite old but so nobee has to bee afraid that the authors clean their product via column chromatography
)
Methylation of hydroxy aldehydesArch. Pharm., 1933, 271, 462-466
(
http://www.angelfire.lycos.com/scifi2/lego/journals/28.djvu)
Translated excerpt[...]
The reaction products (alkylated aldehyde and unreacted hydroxy aldehyde) are so pure that further purification (recrystallization or distillation) is only necessary in a few cases.
Dihydroxaldehydes can alkylated in this way, too. Yields are not as high because the formation of mono-alkylated and oxidized products.
Lacking enough starting material we were not able to develop a general method but there is no doubt that this method can be used with sucess for the alkylation of dihyroxy and polyhydroxyaldehydes.
[...]
Veratric aldehyde, 3-4-dimethoxybenzaldehydeTo 15.2 g vanillin (0.1 mol) a calculated amount of kalihydrat (
probably KOH) was added and dissolved in 75 ml MeOH. 18 g methyl tosylate (0.1 mol) and heated on a water bath for 1.5 h to reflux. As soon as the the light yellow, clear solution starts boiling the potassium salt of methyl toluenesulfonic acid starts to precipitate. After 1.5 h everything is poured in about 300 ml of H
2O. First there is a white emulsion which starts to separate a light yellow oil. The aqeuous solution and the oil is extracted exhaustive with Et
2O, the organic phase is washed twice with 10 ml 5% aqeuous KOH to remove unreacted vanillin. The organic phase turns almost colourless, the alkaline solution is light yellow. The organic phase is washed with H
2O, dried with freshly sulphate (
probably MgSO4 or Na2SO4) and evaporated. The oily residue solidifies on cooling (melting point: 42-43°C).
Recrystallization from Et
2O yields a white product. Yield: 13.8 g, 83% of theory.
The pooled basic solutions and wash water is acidified with 20% H
2SO
4 and extracted with Et
2O. The organic phases are dried with Na
2SO
4 and treated as usally.
The yield of light yellow coloured vanillin (melting point: 81-82°C) is 2.5 g (increasing the yield to 99%) and it can be used without further purification.
Vanillin ethyl ether, 4-ethoxy-3-methoxybenzaldehyde5 g vanillin were treated with 150 ml EtOH containing 2 g 90% KOH. 6.6 g ethyl toluenesulfonic acid are added and the reaction mixture is refluxed for 1.5 h. The still hot solution is poured in 600 ml H
2O and proceeds as describe above.
Yield of ethyl vanillin (
this must be an error, ethyl vanillin is 3-ethoxy-4-hydroxybenzaldehyde, the probably mean ethylated vanillin): 4.9 g. 0.9 g vanillin are recovered. Total yield: almost 99%.
Amyl ether of vanillin, 4-pentoxy-3-methoxybenzaldehyde5 g vanillin are dissolved in 50 ml EtOH containing 2 g KOH (90%), then treated with 8 g amyl toluenesulfonic acid and refluxed for 2 h. The reaction mixture is poured in the 4-times amout of H
2O and a heavy oil precipitates. The mixture is extracted with Et
2O, the organic phase is washed two times with 5% alkali solution (
any basic solution will work, not specified here), then with H
2O and dried with Na
2SO
4. After evaporation a light yellow oil is obtained. After rectification one gets 5 g of a water-coloured (boiling point 185-186°C (17 mm)).
1 g vanilin was recovered from the wash water and alkaline solutions.
Total yield: 86%.
o-Methxoybenzaldehyde12.2 g Salicylaldehyde (0.1 mol) are dissolved in 100 ml ethanolic KOH-solution, the solutions turns slightly green, 18.6 methyl toluenesulfonic acid are added and the solution is refluxed for 1.5 h.
The reaction after usual workup yields 10.5
o-methoxybenzaldehyde and 2.7 g salicylaldehyde.
Total yield: ~87%.
o-EthxoybenzaldehydeThe reaction is carried out as above but with ethyl toluenesulfonic acid. From 12.2 g salicylaldehyde 2.5 g are recovered. 11.5 g of ethoxy compound are obtained. Total yield: ~96%.
4-Methoxybenzaldehyde6.1 g
p-Hydroxybenzaldehyde are dissolved in 50 ml of n-ethanolic potash lye, treated with 9.3 g methyl toluenesulfonic acid and heated to reflux on the water bath. After usual workup one gets 4.1 anisaldehyde. 2 g
p-hydroxybenzaldehyde are recovered. Total yield: 90%.
Veratric aldehyde from protocatechualdehyde, 3,4-dimethoxybenzaldehyde from 3,4-dihydroxybenzaldehyde5 g protocatechualdehyde are dissolved in 72 ml n-ethanolic potash lye, turning the solution instantly greenish-brown. 13.6 g methyl toluenesulfonic acid are added and the mixture is refluxed for 1.5 h on the water bath.
After usual workup one gets 3.5 g veratric aldehyde (melting point: 42-43°C). Yield: ~60%.
The ethanolic washing solutions after acidifying and extraction with Et
2O yielded 2 g of dark crystalline product which is a mixture of the starting material and the monomethyl ester (
probably the monomethylated product is meant).
Due to the lack of starting material and the difficulty of separating such mixtures we were not able to dertemine the quantitative relation.