Methylene Sulfate

[lugh]

Baker published this in JCS 1765 (1931)

The methods available for the methylenation of aromatic o-dihydroxy compounds to the methylenedioxy compounds are unsatisfactory. The reaction has invariably been carried out by the action of dihalogenomethanes an the alkali salts of catechol and derivatives. The so-called methylene sulphate is here shown to be a satisfactory agent for tlie methylenation of o-dihydric phenols, monohydric phenols, alcohols, and glycols.
Methylene sulphate has been described, was first prepared by Delepine (Compt. rend 129, 831 ( 1899); Bull Soc chim 21 1055 (1899) by the action of paraformaldehyde on fuming sulphuric acid. He described it as a colourless crystalline solid, mp about 155° (decomposes), which was hydrolysed to formaldehyde and sulphuric acid by heating with water or aqueous alkaline solutions and gave acetals of formaldehyde when heated with alcohols. Methylene sulphate figures incidentally in certain patents for the preparation of aromatic hydroxy-aldehydes (Eng. Pats. 160765, 157850, 161679, 164715), and Delaby Bull Soc chim. 39 1612 (1926) has prepared the methylene ether of thymol by the interaction of sodium thymoxide and methylene sulphate in acetone solution. This author refers to a thesis by Darrigarde (Paris, 1912) in which certain methylene ethers are prepared by means of methylene sulphate, but the work has apparently not been published.
Methylene sulphate has now been prepared by a modiflcation of the methods described by Delepine and Delaby in a yield of over 60%. It is completely stable, can be kept indefinitely, and ean be used in much the same way as dimethyl sulphate. The reactions of this compound may be summarised as follows.
Reaction with o-Dihydric Phenols.-Catechol reacts readily with methylene sulphate in 50% acetone solution in presence of sodium hydroxide to give catechol methylene ether (methylenedioxybenzene), which thus becomes a readily accessible substance. Protocatechuic aldehyde in dilute alcoholic solution similarly gives piperonal, but the yield in this case is not so satisfactory. It was not found possiblc to effect the methylation of protocatechuic acid.
EXPERIMENTAL.
Methylene Sulphate (compare Delepine and Delaby, loc. cit.).-To stirred molten fuming sulphuric acid containing 50% of sulphur trioxide (500 g), finely powdered paraformaldehyde (100 g) is added, the temperature being kept between 60° and 70° (2 hours). After 12 hours the pasty product is drained an a sintered glass filter and, air having been sucked through it for a short time, dropped in portions into a stirred mixture of water and ice. The methylene sulphate is collected, washed with cold water till almost neutral, and dried in the air and finally in a vacuum over calcium chloride; it now consists of small colourless crystals (228 g), mp 155° (partial decomposition when rapidly heated : much slower when slowly heated). Washing the product with alcohol and ether as recommended by Delepine is only necessary for purposes of analysis  Methylene sulphate in small quantities may be crystallised from acetone, paracetaldehyde, methylal, glycol methylene ether, and dioxan; the hot solutions are not very stable.
Catechol Methylene Ether-The methylenation of catechol in benzene containing potassium carbonate, or of its disodium salt in acetone. To a mixture of catechol (80 g) in acetone (300 cc) and sodium hydroxide (80 g) in water (300 cc), air being excluded by a current of coal gas, methylene sulphate (80 g) was added in portions with vigorous stirring, so that the temperature kept at about 45°. After 1 hours stirring, water was added, acetone and catechol methylene ether were distilled in steam, and the layer was extracted with ether; it was obtained as a colourIess oil (22 g)
Piperonal.-Protocatechuic aldehyde (1.4 g) in alcohol (10 cc) was treated with potassium hydroxide (4.9 g) in water (10 cc) and methylene sulphate (4.4 g.), and warms till a vigorous reaction set in. After further heating an the water-bath for 5 minutes, cooling, and dilution with water, crude piperonal (.15 g.) was extracted with ether,  m p 37° after crystallisation from ligroin

Obviously, this route needs to bee optimized  

[terbium]

This, in addition to the citations that PolytheneSam found certainly dispels my disbelief in the existance of "methylene sulfate".

More recent work on the use of methylene chloride as a methylenating agent gives as good or better yields than those reported here for methylene sulfate. This coupled with the ready availability of methylene chloride would seem to make it still the methylenating agent of choice for most people.

[Antoncho]

Obviously, this route needs to bee optimized

But it's still very cute  The biggest problem (for SWIM, at least) seems to bee the oleum...

This is probably much cheaper than DCM, cause of DMSO. Would bee cool for someone who started w/large amts of catechol (followed by, say, chloromethylative formylation)... Sassy, esp. in bulk, is imposssible to get in certain places of the world:))

Antoncho

[lugh]

Catchetol can be made via fusion of phenol with sodium hydroxide, along with resorcinol and phlorglucinol  

The biggest problem (for SWIM, at least) seems to bee the oleum

According to Sidgewick, sulfur trioxide is produced when ferrous sulfate is distilled, it's thought by certain bees that the ferrous sulfate would have to be almost anhydrous to produce oleum  

[Rhodium]

Wouldn't the water of crystallization distill off long before the oleum distillation temperature was reached?

[lugh]

Wouldn't the water of crystallization distill off long before the oleum distillation temperature was reached?

That's why the exsicated form of ferrous sulfate must be used, six of the seven waters are removed when it's dried. 

[Antoncho]

Yes, you're both right - it will get unhydrous to that point, and it is impossible to do at home - because an ordinary gas stove simply doesn't pull that temperature. SWIM tried it twice, both times ruined the flasks (once, after all patience had gone from him, he took away the metallic grid from above (immideately above) the flame - and the flask's bottom melted. Another time it simply cracked as it cooled down.

Also - don't you think that to condense SO3 down from so high a temp., one would need to have a very good condenser? It boils at 40 C!! If a cloud of it escapes into the room, ............... will undoubtedly happen

The more realistic approach is to heat NaHSO4, first it rearranges to Na2S2O7 , which is itself widely available, and then, somewhere circa 300 C, it'll give off SO3. SWIM didn't try it as he beecame pitious of his flasks

Antoncho

[lugh]

Ferrous sulfate septahydrate can be made from iron filings and sulfuric acid, it  loses six water molecules at 90 ° C and the last water molecule at 300 ° C. Anhydrous ferrous sulfate decomposes into sulfur trioxide at 480 ° C. One shouldn't need to condense it, merely cool it enough so that it will condense in as concentrated and chilled sulfuric acid as one can obtain, 50% oleum has a specific gravity of 2.001