Allylbenzene From Benzene
This is the infamous Friedel-Crafts method and works in a manner similar to the previously mentioned method where P2P was made by merging benzene and chloroacetone using AICI3. This method is for speed makers only and is not recommended for conversion of 1,3-benzodioxole. However, this should work in a limited way on catechol. The conversion factor is very low but that isn't a major concern of speed chemists because cheap old benzene is the precursor and all of that benzene that isn't converted can be run back through this simple little process over and over again. Before she knows it, the chemist will have amassed an enormous amount of allylbenzene [139, 140].
Aside of benzene the chemist has a choice in which allyl she can use. Allyl alcohol, allyl bromide or allyl chloride can be used with equal success but allyl alcohol is a nice bonus because it is easier
to make than the other two. All three of these are really cheap to purchase but Strike is going to tell how all three are made in the Chemicals section.
Everything needs to be anhydrous and the procedure begins by chilling 500g benzene, and 80g allyl alcohol to 0°C in a single-neck flask. 90g of powdered, anhydrous AICI3 is added which will cause a violent reaction and heat. A condenser is immediately attached with a tube leading to a water trap and the solution is allowed to come back down to room temperature. The reaction stirs for 6 more hours at room temperature, poured into ice cold dilute HCI solution and the benzene layer separated. When the benzene layer is distilled the first things to come over are perfectly reusable unreacted allyl alcohol and benzene and finally will come the high boiling allylbenzene.
There are a great many aspects to the Friedel-Crafts method that Strike does not have the space to go into. Friedel-Crafts works better if chloro or bromobenzene and their X counterparts are used in place of plain old benzene. Also, there is a significant amount of unwanted byproducts and molecular rearrangements that accompany this sort of reaction. Strike strongly suggests that people read more about this method before they attempt any such reaction.
SAFROLE FROM 1,3-BENZODIOXOLE
SAFROLE FROM 1,3-BENZODIOXOLE
[141, 142]—This is similar to the Friedel-Crafts method but is less harsh and has been proven successful at producing safrole. In a very small flask is added 7.2g of allyl chloride, 34.3g 1,3-benzodioxole and 0.15g powdered Cu (which can be made by reducing a solution of CuS04 with zinc dust). The solution is slowly heated to a mild boil for 10 hours with the temperature kept below 125°C. Some ring scission will have occurred so that phenolic compounds are mixed with the tar, safrole and unreacted benzodioxole. These phenols are removed by shaking the mix with 5% NaOH solution, extracting with ether and fractionally distilling under vacuum to give unreacted 1,3-benzodioxole and Safrole (yield=30%)
There is one other benzene to allylbenzene method that you should take a look at. Osmium sent in the article in which that magical clay and other similar catalyst add the allyl to aryl in record fashion. To read more check out ref #143.
Continue reading here: Isosafrole From Piperonal
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