[jlax31]

Ok, i need a little help here. I just wrote a bunch and found out I can't attach a BMP file so I lost everything. Anyhow..

Rules for this synthesis problem: Benzene and propanoic acid molecules can be the only source of carbons. Any reagent/solvent is allowed.

My attempt at a solution: I'm a little stumped on how to approach this. on both sides of a hexenone is a bromobenzene. How do I get the attachments at the meta position on the benzenes with a bromine? or am i approaching this wrong. Any help is appreciated.

[kriggy]

You can have substiuent on benzene which allows for meta substitution and then substitute if for bromine. I think its called Sandmayer reaction

[Dan]

How do I get the attachments at the meta position on the benzenes with a bromine?

Br is an o/p-director, so that is not going to work. You will have to install a m-director first, then brominate.

[jlax31]

How do I get the attachments at the meta position on the benzenes with a bromine?

Br is an o/p-director, so that is not going to work. You will have to install a m-director first, then brominate.

OK, after some work I may have got most of it. The only problem is where to go from here:

1) I need to attach the propanoic acid to the benzene.I do this by turning the propanoic acid to acetal chloride by a halogen reaction:
CH3CH2COOH + HX -----------> CH3CH2COX + H20

2) Friedel-Craft Acylation of Benzene:
CH3CH2COX + Benzene (with AlCL3 cata) ----------> (Attaches to Benzene) creates a EWG that also meta directs.

3) Since CH3CH2CO is EWG and meta directing I add Br2 (FeBr3 Cata) to it:
Substituted Benzene + Br2 (FeBr3 Cata) ---------> m - bromo, propanal?

Now I can do this again to form the other side of the desired product. However, this is where I am a little confused on how to 'attach' each molecule. I could reduce one carbonyl aledyde, but how to turn it it in to a non conjugated alkene and 'attach'?

Any help is appreciated.

[jlax31]

Did I go completely wrong here? haha

[camptzak]

Did I go completely wrong here? haha

I can't figure this on out either 

I was attempting to build the carbon chain from one side and then connect it with this:
http://www.organic-chemistry.org/namedreactions/heck-reaction.shtm

I was thinking you acylate just as you proposed. then put a grignard reagent on the terminal carbon and react with another molecule of propionoic acid, then convert it to an α,β-unsaturated carbonyl and run the heck. but there are many problems with this and I am not sure if it would even work at all.

[jlax31]

Perhaps the double bonds and six carbon chain are from a third benzene...

[camptzak]

Perhaps the double bonds and six carbon chain are from a third benzene...

I mean you could probably do that, but now we are both getting into routes that are incredibly long and not efficient at all. since this is a test question, there must be an answer that is more sensible.

[orgopete]

Meta substitution and acylaction seem like the route I'd choose. I'd try functional groups changes to get a double bond and enable a coupling reaction.