[kriggy]

Hi there,
Im interested in doing some coupling reactions in the future - I dont know which ones, it will probably depend on which compounds will be available to me but most likely its gonna be suzuki.
After little bit of discussion and wikipedia read I become aware that chloride is the least reactive - compared to triflate/bromide.. How exactly does it show? Does it mean that the reaction does not proceed? The point of my question is that chlorinated compound I would like to use is comercialy available but its the only one. I could probably make brominated compound but it would be bit difficult (Im looking for ortho-phenylenediamine substitued in positions 4 and 5)
Im just checking my options before I start doing something and waste time / money on something that is not working.

Thanks for help/suggestions.

[Enthalpy]

Hey Kriggy 

will you make a fibre of it? Like that
and so on
the macromolecule is almost straight, and neighbour macromolecules make hydrogen bridges, just like in Kevlar.
(Maybe the ol' Stephanie had tried that one already)
Stretch it during the production. With the secondary amines, you could also cross-link the macromolecules, say with a peroxide - something aramides can't.

[kriggy]

haah cool idea but sadly, no

The point is  that I need my (3,5 substitued) phenylene diamine as reagent in multistep synthesis and by the different substituents I get different compounds in the end and hopefuly with some biolgogical activity. I need the phenylene diamine in the 1st step out of 4 or 5 and all of the amines are freaking expensive and available in low amounts (like 25 mg for some 100 euro from sigma). So I was thinking I could do the synthesis with chlorinated amine and then do some coupling reactions to go areount the multi-step process and quite expensive reagents.

[Enthalpy]

OK then, I pack up again my epoxy, the formaldehyde as well, and don't buy two tickets for Stockholm. 

More for my personal information:

Tricks exist to replace a chlorine with an iodine. Something like: have some iodine salt (sodium?) in a solvent where the chloride isn't soluble; pour the organic chloride in the solution, the chloride precipitates and the iodine bonds with the organic part. Could that work despite the amines on your phenyl?

[kriggy]

Like Finkelstein reaction?
Maybe, there is Cu(I) catalyzed version that should work on aromatics but it seems to work only with bromides which I need to make OR is super expensive.

Anyway, so far it looks I will stay with classic ochem2 exam sequence: nitration -> diazotation -> Sandmeyer reaction or some coupling using diazonium salts. (And hope that there will not be much of steric hinderance )

[Enthalpy]

Treat the chloride with gaseous Cd or Zn to obtain a more reactive R-Cd-Cl or R-Zn-Cl?
http://www.chemicalforums.com/index.php?topic=72951.msg287717#msg287717
yes, that's speculative, but a trial looks rather easy to my untrained eyes. Then the R-Cd-Cl might react with Br₂ or directly with the groups you want.

[kriggy]

Im not sure If we have equipment for doing this kind of stuff. :-D
Anyway What are some reliable reductions for aromatic nitro to amino group? I mean I know some like H₂+kat, Fe+HCl, SnCl₂.. But I would prefer not to work with hydrogen and heard that removing Sn salts from the mixture is pain.
Maybe beshamp reduction or Na₂S₂O₄?
Im sorry, maybe this sounds stupid but actualy I know the methods that can be used, but I never actualy did any of them so I cant realy compare which one is the best or know their limits

[Enthalpy]

Build the equipment! Make a hermetic pot of cadmium, evacuate it, heat it to 250°C, introduce your chloride slowly to less than 1Pa. But why your amines wouldn't mess with the rest at that point is very obscure to me.

OK, you don't want to experiment that, right?

Would it be possible to swap the roles of the chlorines and amines in your phenyl? The -Cl can be replaced by -NH₂ (can't  they?) so you might perhaps make the couplings at the original -NH₂ instead, before or after transforming the Cl. Either use the -NH₂ directly, or transform them before into -NO₂, -OH, -Br... Would that make any sense? (And apologies if not)

[kriggy]

I need to have the amino groups for condenstation in the reaction sequence

this is the 1st step of 4 or 5 and I wanted to be able to put different R substituents into the molecule in a way, that I dont have to repeat the whole sequence again and again.
That was the point of my original question, since the amine where R=Cl is available comercialy but then the Cl is considered the worst leaving group in coupling reactions.

[Dan]

Anyway What are some reliable reductions for aromatic nitro to amino group? I mean I know some like H₂+kat, Fe+HCl, SnCl₂.. But I would prefer not to work with hydrogen and heard that removing Sn salts from the mixture is pain.

My personal favourite is Zn/CuSO₄.

There is a procedure in the Supporting information of this paper (compound 16, page S33).

There are catalysts for Suzuki reactions and Buchwald-Hartwig aminations that work with aryl chlorides (a lot of work on this was done by the Buchwald and Hartwig groups) - these catalysts have been around for almost 20 years now, so you should be able to find something that works. It might be expensive or require you to prepare the catalyst/ligand yourself though.

Pd and Cu catalysed halogen exchange may also be an option worth investigating. I know this is well known for ArBr ArI, but I expect someone has managed it with ArCl by now (though I can't remember off the top of my head). Search for the Buchwald "aromatic Finkelstein reaction" to get started.

[Enthalpy]

- 1,2,4,5-tetrabromobenzene is affordable
- Bromine may be easier than chlorine for subsequent use
- Sodium amide is affordable too
- At least bromobenzene is known to react with sodium amide to make aniline

so would limited sodium amide produce diamino-dibromo-benzene?

Err, I realize that the chances to obtain some 1,2-diamino-4,5-dibromo are slim (the amine doesn't even appear where the bromine was), and that sodium and potassium amides have definite drawbacks. Magnesium amide  doesn't look common. So, apologies in advances if I put nonsense.

[Enthalpy]

Fun: someone has made nearly the suggested ladder polymer.

Synthesis and characterization of thermally stable polymers containing phenazine
H.M. Gajiwala, R. Zand
http://www.researchgate.net/profile/Robert_Zand/publication/222516007_Synthesis_and_characterization_of_thermally_stable_polymers_containing_phenazine/links/00b4952543a13769ab000000.pdf

From tetraaminobenzene and dihydroxybenzoquinone, they obtained more double bonds at the nitrogens hence fewer hydrogen bonds between the macromolecules, but the polymer decomposed at 400°C, not bad. Said to be brittle and form dendrites, which suggests to make fibres of it.

I wonder what hydrogen bridges or cross-linking can do to that stuff.