Virtualquestion
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From THF to BDO
Hi there
First of all, sorry for my weird writing, I'm not a native speaker.
What do you think about this idea: Refluxing 1 mol of THF in about 1,3 mol of 20% Hydrochloric acid (20% because everything above would lead the
excess of HCl to outgas -->nasty) --> This should lead to
4-Chlorobutane-1-ol in a pretty good yield, maybe some 1,4-Dichlorobutane will be formed, but thats not a problem. Then so much 30% NaOH is added that
the excess of Hydrochloric acid is neutralized and there is still enough NaOH to form 1,4-Butanediol by refluxing the mixture. As soon as the reaction
is completed you probably gonna see it because of the size and the appearance of the drops, because the BDO will not boil at this temperature, only
the 4-Chlorobutane-1-ol will. And as soon there's no more
4-Chlorobutane-1-ol, the water is going to boil and form these characteristic drops. After the reaction is completed the BDO is then going to be
extracted with TBME or Diethylether for example wich should work just fine because of all the NaCl in the water from the reaction. In case of the BDO
staying in the water, more NaCl is added. And then standard procedure, drying, filtering and getting rid of all the Ether. This should be possible in
only one pot, aside from the extraction process.
What do you think?
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Melgar
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You'd probably need hydrobromic acid for decent yields. I don't think hydrochloric acid would work, but hydrobromic might.
The first step in the process of learning something is admitting that you don't know it already.
I'm givin' the spam shields max power at full warp, but they just dinna have the power! We're gonna have to evacuate to new forum software!
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PirateDocBrown
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Yeah, chloride is not particularly polarizable, and so is unlikely to participate in Sn2 cleavage of the ether bond.
Bromide would indeed be better, and iodide better still. They are just stronger nucleophiles.
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Metacelsus
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I have occasionally observed THF ring opening in the presence of thiolate nucleophiles. The reaction is something that I had been trying to avoid,
since I was trying to trap the thiolate (formed in situ via reaction of a carbanion with elemental sulfur) with a different electrophile. The ring
opening doesn't happen at -78 °C, but does happen to some extent if the mixture is warmed to 0 °C.
It might be possible to use sodium or potassium sulfide to ring-open THF. However, getting to butanediol from the product would be difficult.
You could also try heating THF with aqueous KOH (this reaction might need high temperatures/pressures, however).
1,4-butanediol is miscible with water and I don't think an aqueous/organic extraction would be feasible. You would likely need to do a (vacuum)
distillation to isolate your product.
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Boffis
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There are numerous published examples of the preparation of dibromo and diiodo butanes from THF, check out Vogel. The simplest route may be sodium
bromide and sulphuric acid if you don't have 48% hydrobromic acid. In Arun Sethi's book there is a preparation of 1,4-di-iodobutane from THF with KI
and phosphoric acid too. You need phosphoric acid with iodide because sulphuric acid liberates free iodine under these conditions but the bromo
synthesis can tolerate some water in the reaction mixture which reduces the tendency of the acid to oxidize the HBr that forms as an intermediate. You
can also use Br + red phosphorus is you have access to the later.
I have just prepared a small amount of 1,4-dibromobutane en-route to butylene-bis(thiuronium bromide) but I started with 1,4-butanediol which, up to
about a year ago, was available off Ebay.
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BromicAcid
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I used to have a reaction I ran in anhydrous conditions with hydrogen chloride and THF. One of the impurities in the final product was a
chlorobutanol, and it had to be recrystalized away form. However, amounts were not that high and it was mostly an impurity in trace amounts.
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Virtualquestion
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Thank you very much for your answers!
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Dope Amine
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It was my understanding that sulfuric acid/H2O should work. No?
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