November 24, 2024, 08:56:26 PM
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Topic: Is it possible to add an alkyl group to a deactivated benzene ring?  (Read 2708 times)

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Offline Wingpin

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The only method I remember of adding alkyl groups to a benzene is Friedel-Crafts, but that doesn't work on deactivated rings from what I have learned.
I'm looking to form: http://www.chemfrog.com/chemical_info/388406/
from benzene.

The isopropyl group forms from rearrangement of n-propane due to carbocation stability issues, and that can be added reacting propyl chloride and AlCl3 with benzene. But then that would activate the ring, and I won't get my desired meta-director.
On the other hand, if I react an acyl chloride / AlCl3 and benzene I would get a meta-director, but then I wouldn't know how to add the isopropyl group. Not only that, but I wouldn't be sure on how to cleave the ethyl group that would form after removing the oxygen by Wolff-Kishner reduction.
I'm not allowed to utilize the Gatterman-Koch reaction to form benzaldehyde since that was not covered in class.

Assuming I do has both the isopropyl group and methyl group meta to each other, then I still would have the issue of NBS/heat favoring the bromination the isopropyl group rather than the methyl group because of free-radical stability.

Any ideas on how to tackle the problem?
Thanks for the read / help.

Offline Hunter2

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I would start with  2-Phenyl-ethyl-acetate  => with this  do Friedelcrafts with Isopropyl bromide. The Alkyl group is in. The hydrolyse the ester and the remaining alcohol treat with PBr3.

Offline TheOrganic

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Remember, F.C reaction can be controlled kinetically or thermodynamically to get desired products.
For example, F.C. alkylation of Toluene under thermodynamic conditions produces meta-xylene as the major product.

Can you think why? Can you utilize that in this synthesis?

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