mnick12
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Looking for synthesis of 1-bromo-2,6-diisopropylbenzene
Hi,
So I am looking to make a ligand from 1-bromo-2,6-diisopropylbenzene. Unfortunatly the material is quite pricey ~50/g USD from sigma.
I was wondering if anyone had a synthesis for the material in quesiton? Ideally I would like to start from 2,6-diisopropylaniline since I have around
200ml of it. I was thinking a sandmyer reaction, but after looking around for a bit I could not find a prep anywhere online.
Does anyone know of prep for this material? And if not, could anyone offer some advice on trying out the sandmeyer?
Thanks,
mnick
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Eddygp
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Well, the amino group in 2,6-diisopropylaniline is your only worry (before reading that you had that reagent, I was seriously thinking about how to
get the two isopropyl groups with good yields). Right.
You could add sodium nitrite to the 2,6-diisopropylaniline, as well as HCl, to have some sort of substituted benzenediazonium compound (you can use
HNO2 instead of NaNO2). The great thing about the 2,6-diisopropylbenzenediazonium (~chloride) is that you can add NaBr to get
the bromo in the position 1. This gives you your desired compound.
there may be bugs in gfind
[ˌɛdidʒiˈpiː] IPA pronunciation for my Username |
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CuReUS
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HNO2 does not exist in free state.You can't store it in a bottle
| Quote: | | The great thing about the 2,6-diisopropylbenzenediazonium (~chloride) is that you can add NaBr to get the bromo in the position 1. This gives you
your desired compound. |
just because the ring is activated doesn't mean that NaBr can be used like using KI for iodination.since I2 can act as both oxidising and
reducing agent,it can be used,but not Br2
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Chemosynthesis
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Quote: Originally posted by CuReUS  |
just because the ring is activated doesn't mean that NaBr can be used like using KI for iodination.since I2 can act as both oxidising and
reducing agent,it can be used,but not Br2 |
Don't be silly. He said NaBr, not Br2.
Though the paper uses slightly different substrates, salts and catalysts, which may change things, there is definitely a precedent for this type of
Sandmeyer reaction:
Synthesis 2007(16): 2534-2538
This is usually taught as CuBr, though.
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mnick12
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| Quote: Originally posted by Chemosynthesis | | Quote: Originally posted by CuReUS |
just because the ring is activated doesn't mean that NaBr can be used like using KI for iodination.since I2 can act as both oxidising and
reducing agent,it can be used,but not Br2 |
Don't be silly. He said NaBr, not Br2.
Though the paper uses slightly different substrates, salts and catalysts, which may change things, there is definitely a precedent for this type of
Sandmeyer reaction:
Synthesis 2007(16): 2534-2538
This is usually taught as CuBr, though. |
I have read a few of the diazo reactions on orgsynth, and it looks pretty straight foward. I was just curious to see if there were any synthesis in
the lit before I went off and decided to do it myself.
I did however, find in an rsc communication that the iodobenzene can be made in 60% yield using the diazo and KI. Unfortunatly it was only a
communication, and did not give any experimental conditions.
I may try to make the iodo compound anyway since it will be more active in substitution reactions.
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mnick12
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Removing iodine
Well,
I decided to make to make the iodobenzene instead, since no Cu salts are needed and you can use HCl.
Anyway diazotization went fine, and I got a nice clear orange solution. Upon addition of the KI solution, it went purple as N2 was released. After
stirring overnight at rt a large black glob sank to the bottom. The scale of this rxn was around 3mmol.
Anway I did a steam distillation and collected ~210ml of distillate. Unfortunately I forgot to make the solution alkaline before distillation so the
the distillate was black/purple. After extraction with DCM I washed 2x with 2M NaOH, and 2x with 1M HCl. After pulling off the DCM in the rotovap I
was left with a dark black/red oil.
I decided vacuum distillation would be best, apparently this material boils at 98-101C @ 1 torr. I didnt look at the vacuum being drawn, but my
product came over at 146-151C.
The problem is it is still black. The left over iodine vaporized and condensed in the condensor. Then, as the distillate came over it dissolved the I2
making the distillate black.
Does anyone have any suggestions how to remove the excess I2? Keep in mind this will be going on to react with an alkyl lithium so aqueous solutions
are a no no.
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Chemosynthesis
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Those labile iodines can be quite annoying. Consider stirring with activated charcoal/decolorizing carbon.
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mnick12
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Well I decided to give in and wash with an aqueous thiosulfate solution, and it cleared the iodine right up! I ended up extracting the organics
afterwards with toluene and dried them over Na2SO4.
Removal of the toluene under vacuum gave a nice light brown oil, and the 1H-NMR looked pretty good except for a septet upfield of where the normal
isopropyl protons should be.
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