[Starksays]

I'm working a synthesis problem and if I make 2-chloro-1,3,5-trimethlybenzene I know how to convert the chloride into the carboxylic acid I need. My only trouble is creating 2-chloro-1,3,5-trimethlybenzene from benzene? Suggestions or help would be much appreciated.

[discodermolide]

I would be interested to know how you want to turn the chloro group into a carboxylic acid.

[Starksays]

Well isn't there a way by using cyanide and then hydrogenation? If that wouldn't work maybe instead of a trimethyl benzene with a halogen I could make a trimethyl phenol and then use an oxidizing agent. Either way making a trimethyl benzene with a subsituent between two of the methyl's without using Diels-alder seems impossible to me but I need to do it using benzene as my starting material.

[discodermolide]

I don't think you can displace the Cl with CN. Hydrogenation of CN does not produce a carboxylic acid. Oxidation of phenol will also not produce a carboxylic acid.
But there is a way!
Making trimethylbenzene should be easy.

[Starksays]

Could I treat benzene with CO/CuCl/AlCl3/HCl to make benzaldehyde then Zn(Hg)/HCl to make toluene.

Then do way too many steps to make a xylene and ambigiously make mesitylene from this xylene. So I'm not exactly sure how this is easy or what to do after that to get the carboxylic acid?

[discodermolide]

Forget that for the moment.
How do you make 1,3,5 trimethylbenzene?
http://en.wikipedia.org/wiki/Friedel–Crafts_reaction

[Starksays]

Benzene + CH3Br + AlCl3?

[discodermolide]

OK, I think that would work.
This should be your final product, correct?

[Starksays]

That is what I aim for.

[discodermolide]

OK, having made your trimethylbenzene, what next?

[Starksays]

Well you said hydrolyzing benzonitrile wouldn't work. And as it isn't a primary alcohol I can't oxidize. Not to mention any O's could start changing methyls. Would bromination, followed by a grignard followed by Carbon dioxide work?

[discodermolide]

Yes, carbonylation of the Grignard from the corresponding trimethyl bromobenzene.

[Altered State]

Yes, carbonylation of the Grignard from the corresponding trimethyl bromobenzene.

Would you be able to detail the last steps of the process?

You have trimethyl bromobenzene, add Mg, and then what?
If you add H3C-C(O)-CH3 you obtain alcohol, not carboxilic acid, as far as I'm concerned.

[discodermolide]

Yes, carbonylation of the Grignard from the corresponding trimethyl bromobenzene.

Would you be able to detail the last steps of the process?

You have trimethyl bromobenzene, add Mg, and then what?
If you add H3C-C(O)-CH3 you obtain alcohol, not carboxilic acid, as far as I'm concerned.

No one mentioned acetone. If you treat a Grignard reagent with carbon dioxide you obtain a carboxylic acid after work-up.

[Altered State]

Yes, carbonylation of the Grignard from the corresponding trimethyl bromobenzene.

Would you be able to detail the last steps of the process?

You have trimethyl bromobenzene, add Mg, and then what?
If you add H3C-C(O)-CH3 you obtain alcohol, not carboxilic acid, as far as I'm concerned.

No one mentioned acetone. If you treat a Grignard reagent with carbon dioxide you obtain a carboxylic acid after work-up.

Thanks, that last step was the one I didn't get.