04-05-02 22:12
No 292954
(Rated as: excellent)

(Official Hive Translator)
04-06-02 09:37
No 293193
(Rated as: excellent)

What a strange coincidence....

This one is not exactly the same - it's about 2,6-diMeO-4-allylphenol.

Funny how a slightly different rearrangement technique produces a different isomer. 1 hr vac. reflux vs. heating in a sealed ampule at 150 C for a weeksmile.

Plus - a bonus track! - isomerization to propenylbenzenesmile

Preparation of 1,3-dimethoxy-2-hydroxy-benzene.

[See Krauss and Creed, J. Am. Chem. Soc. 9, 1433 (1017) ]

A flask containing 126 parts of pyrogallol is connected to a reflux condenser. Methyl bromide is passed into the flask by a glass tube ending in a capillary and passing through the condenser to near the bottom of the flask until the air is displaced. A solution of sodium methylate (prepared by dissolving 57.5 parts of sodium in 640 parts of absolute methanol) is run into the flask together with a continuous stream of methyl bromide. The flask is heated on the water bath and the current of methyl bromide continued until the reaction is nearly neutral. The gas is rapidly absorbed and sodium bromide separates. The 1,3-dimethoxy-2-hydroxybenzene is isolated as follows. Water is added until the sodium bromide dissolves. The methanol is evaporated, and the residue is distilled with steam. Any 1,2,3-trimethoxy-benzene present passes over in the steam. The residue is acidified and extracted with ether. The ether solution is evaporated and the resulting oil fractionated under reduced pressure. The pure 1,3-dimethoxy-2-hydroxybenbene is obtained as white crystals melting at 55 56 C.



A mixture of 154 parts of 1,3-dimethoxy-2-hydroxybenzene, 133 parts of allyl bromide and 180 parts of anhydrous potassium carbonate in  400 parts of dry acetone was heated to boiling under reflux with occasional shaking for eight hours. The solvent was removed by distillation, and the residue was diluted with water and extracted with ether. The ether was washed with dilute sodium hydroxide solution then with water, dried with calcium chloride and distilled under reduced pressure on the steam bath to remove ether and excess allyl bromide. The residual liquid was distilled under high vacuum and was obtained as an almost colorless oil distilling at 102/2 mm and 30/9 mm. The index of refraction was n1.5300. The yield of 2-allyloxy-1,2-dimethoxybenzene was 184 parts or 95%.

EXAMPLE III : 3,5-dimethoxy-4-hydroxy-allylbenzene

2-allyloxy-1,3-dimethozybenzene (104 parts) was boiled under reflux at 75 mm. pressure for one hour and was then distilled under high vacuum. 3,5-dimethoxy-4-hydroxyallylbenzene distilled as a colorless oil boiling at 123 125 C /2 mm Hg 1.5478. The yield was147 parts or 90%.


3,5-dimethoxy-4-allyloxypropenylbenzene, as a salt

A mixture of 100 parts of 3,5-dimethoxy-4-hydroxyallyl benzene, 50 parts of potassium hydroxide and 200 parts of water was placed in a flask connected to a distillation assembly and heated to boiling. The clear solution soon became thick with precipitate. When the temperature reached 110 C it had set to almost a solid. At this point 450 parts of aniline were added and the mixture distilled again. After about 100 parts of distillate were collected the solution became very thick with precipitate.

This precipitate disappeared when the last bit of water was removed and the temperature began to rise; about 150 parts of distillate had been collected at this point. The distillation was continued until approximately 100 parts of aniline were collected and the temperature of boiling was 178 180 C. The hot mixture was allowed to cool and a mixture of aniline and the potassium salt of 3,5-dimethoxy-4-hydroxypropenyl-benzene solidified.

EXAMPLE V: 3,5-dimethoxy-4-hydroxy-propenylbenzene

The solid mass from Example IV was dissolved in water and extracted with ether. The alkaline aqueous layer was acidified with dilute hydrochloric acid. The oil which separated was extracted with ether and the ether solution was washed with dilute hydrochloric acid, then with water, and then dried. The ether was removed by distilIation and the residual oil was distilled under high vacuum. to give 93 parts of 3,5-dimethoxy-4-hydroxypronenylbenzene to an almost colourless oil boiling at 107-8 /0.05 mmHg.

P.S. The continuation of this amazing patent can bee found in Post 293365 (Antoncho: "Double bond ox. cleavage (to aldehyde) with CuO", Chemistry Discourse)

Note that in the 1st procedure - selective methylation - an absolutely cool one, may i note! - there isn't a yield specified. Besides, there definitely is some more interesting info on this methylation route in the original article.

So, please, can someone look up/upload JACS 39, 1433 (1917)? I shall personally bee infinitely grateful to the one who does it (as SWIM has an immediate practical interest in this method).

(Hive Bee)
04-06-02 12:45
No 293234
      And off we go to the univercity. Give me 30min  Bookmark   

And off we go to the univercity. Give me 30min
(Hive Bee)
04-06-02 13:28
No 293241
      I guess this is it right ??  Bookmark   

I guess this is it right ??

One mole pyrogallol is placed in a flask connected with a reflux condensor. The flask is then filled with methylbromid until all the air is displaced.
2 mole Na is dissolved into 20mole methanol and run into the flask under MeBr gass. The flask is then heated on a watherbath under a continuous steam of MeBr, the current of alkylhalid is continued until the reaction is nearly neutral. The gass is rapidly absorbed and NaBr settles out.

Wather is thn added until the NaBr dissolves, the MeOH is evaporated and the residue is steamdestilated.. Anny trimethylethar will pass over with the steam. The solution is then acidified and extracted with ether, the concentrated in vaco and destilated in vaco. Bp at 1 atm. 250C

As usual the hive book search will charge your hive account with 0.25 carmapoint's
(Official Hive Translator)
04-06-02 14:37
No 293256
      :)  Bookmark   


Thank you, Hest - how sweetsmile! What was the yield, though? Mean, how selective this is?

And sorry about posting those graphics - just couldn't bring myself to type that all in. That's understandable, i guesslaugh.

A question - would it bee correct to assume that in the 1st link, submitted by Natrix - where allyloxy-ortho-diMeObenzene is rearranged to metha-allylsyringol, the rearrangement 1st takes place to para-position and then the allylgroup just migrates to metha-position over the week at 150 C?

(Hive Bee)
04-06-02 15:55
No 293273
      No yeald's Wath's wrong with the 'usual' ways ...  Bookmark   

No yeald's

Wath's wrong with the 'usual' ways (vanilin to tmba, hydroquinon to dimethoxybenzen ect. ??)
(Official Hive Translator)
04-06-02 22:30
No 293367
      Nothing really...  Bookmark   

.... just curious.

P.S. The continuation of this amazing patent can bee found in Post 293365 (Antoncho: "Double bond ox. cleavage (to aldehyde) with CuO", Chemistry Discourse)

P.P.S. Oh, yes - the ref. Patent US2516412