Easy(er?) chloromethylation

[ChemicalSolution]

This one is from Organic Synthesis CV3 195.

In a 3-l. three-necked flask, fitted with a reflux condenser and Hershberg stirrer, are placed 256 g. (2 moles) of naphthalene, 110 g. of paraformaldehyde, 260 ml. of glacial acetic acid, 165 ml. of 85% phosphoric acid, and 428 g. (362 ml., 4.2 moles) of concentrated hydrochloric acid. This mixture is heated in a water bath at 80–85° and vigorously stirred for 6 hours.
After the mixture has been cooled to 15–20° it is transferred to a 2-l. separatory funnel and the crude product is washed first with two 1-l. portions of water cooled to 5–15°, then with 500 ml. of cold 10% potassium carbonate solution, and finally with 500 ml. of cold water. The product is the lower layer in all the washings. After the addition of 200 ml. of ether, the solution is given a preliminary drying by being allowed to stand over 10 g. of anhydrous potassium carbonate, with frequent shaking, for 1 hour. The lower aqueous layer which forms is separated, and the ether solution is again dried over 20 g. of potassium carbonate for 8–10 hours and.
The dried solution is distilled, first at atmospheric pressure to remove most of the solvent, and then under reduced pressure. A fore-run of unused naphthalene amounting to 35–40 g. is collected at 90–110°/5 mm. This is followed by 195–204 g. of 1-chloromethylnaphthalene which boils at 128–133°/5 mm. or at 148–153°/14 mm. (74–77% based on naphthalene consumed) and.

[ChemicalSolution]

And with that......

In a 1-l. flask fitted with a reflux condenser are placed 106 g. (0.6 mole) of 1-chloromethylnaphthalene2, 168 g. (1.2 moles) of hexamethylenetetramine, 250 ml. of glacial acetic acid, and 250 ml. of water. This mixture is heated under reflux for 2 hours. In about 15 minutes the solution becomes homogeneous, and then an oil starts to separate. After the reflux period, 200 ml. of concentrated hydrochloric acid is added and refluxing is continued for an additional 15 minutes. After cooling, the mixture is extracted with 300 ml. of ether; the ether layer is washed three times with 100-ml. portions of water, then with 100 ml. of 10% sodium carbonate solution, and again with 100 ml. of water. The ether extract is dried with about 15 g. of anhydrous sodium sulfate and filtered, and the ether is removed by distillation. The residual liquid is distilled under reduced pressure, the distillate being collected at 105–107°/0.2 mm. or 160–162°/18 mm. The yield of colorless 1-naphthaldehyde freezing between 0.0° and 2.5°  is 70–77 g. (75–82%).


The checkers found that crude chloromethylnaphthalene obtained from the preparation in Organic Syntheses2 could be used with good results. Naphthalene, paraformaldehyde, hydrochloric acid, and phosphoric acid are heated under reflux according to the procedure described. After the crude product is washed with water, 10% potassium carbonate, and water, it is dissolved directly in 500 ml. of glacial acetic acid, diluted with 500 ml. of water, and treated with hexamethylenetetramine by the procedure described above. The over-all yield of almost colorless 1-naphthaldehyde is 162 g., b.p. 162–164°/18 mm.; nD25 1.6503 (52% yield based on naphthalene).
In this variation of the preparation, it is best to use a wide-bore tube as a condenser to remove the unreacted naphthalene. After the naphthalene has been distilled, the wide-bore tube is replaced with an ordinary condenser and the naphthaldehyde is distilled in the usual manner.

Any procedure that eliminates the timely distillation of some MD-chloro compound with an un-godly high bp works for SWIM.

[element109]

I wonder if this would also work well on 1,4-dimethoxybenzene ?

e109

[ChemicalSolution]

SWIM doesn't even know if this will work on benzene.. But she'll let you know..

She will also try benzodioxole..

Julia

[Antoncho]

Hey, guys'n'girls, UTFSE, UTFSE - you'll find a ton of useful info on this topic here.

1,4-MeO-benzene, benzodioxol and benzene have very different properties and need completely different conditions.

For 1,4-DMB such conditions weren't found as yet.

I might have some additional excellent info, if i have time i post it later.

Antoncho