[bigdog101]

Fairly new to retrosynthetic analysis and after some reading, I understand the concept and have managed to successfully design a forward synthesis for some simple target molecules. However, there is a target molecule that I'm having trouble with. Any advice/help for the following would be greatly appreciated.

[Babcock_Hall]

It is a forum rule that you must show your attempt first before we can help you.  A good place to start might be to discuss what you know about ortho/para- versus meta-directing substituents.

[bigdog101]

Well when there is a benzene ring with some substituent present then there are different possible structural isomers. Adjacent groups are referred to as ortho-configuration, one carbon further meta-configuration and opposite sides of the ring is para-configuration. If I remember correctly, electron donating groups are ortho/para directing groups and electron withdrawing are meta directing groups.

[Babcock_Hall]

Is chlorine o,p-directing or m-directing?

[bigdog101]

o,p-directing as it donates electrons

[Babcock_Hall]

OK, so if you started with benzene and added substituents could you chlorinate first, and then add another group?

[bigdog101]

yes?

[Babcock_Hall]

No.  Based on our conversation so far, why not?

[bigdog101]

Can you explain please. I don't know if it's because I've been sat at my laptop for the past 8 hours but I'm a bit brain dead 

[Babcock_Hall]

If you add chlorine to benzene first, the next group is directed to an ortho or para position.  The two groups in your target have a meta relationship.

[bigdog101]

Thanks, understood. In that case, am I right in saying that the first disconnection would be N(CH₃)₂ ?

[Babcock_Hall]

If you mean that you plan to add that group last, then that sounds reasonable.  How will you do so?

[bigdog101]

So if I'm correct the disconnection of N(CH₃)₂ will give the two synthons shown but I'm unsure as to what the synthetic equivalents will be? would a H on the N and a Cl on the carbocation work?

[kriggy]

Well it could work. Then the question is, how do you prepare that ?

[bigdog101]

An acyl chloride?