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Topic: Could anyone help with this synthesis?  (Read 2453 times)

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Offline quantumnumber

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Could anyone help with this synthesis?
« on: August 23, 2014, 03:53:33 PM »
Hi guys,

Could anyone help with this synthesis? My problem are the two cloro substituents. I can only use benzene, toluene, and simple aliphatic compounds with four carbon atoms at the most.

I thought two ways, two different FGI, but I'm not sure they'll work. I attach my proposals... but certainly I'm quite lost with this.
By the way, is it possible to halogenate twice a ketone (as I try to do in the second proposal?
  ???

Many Thanks!

Offline CrazyAssasin

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Re: Could anyone help with this synthesis?
« Reply #1 on: August 23, 2014, 04:31:00 PM »
First one is okay, while in the second case as you are doing halogenation firstly two chlorine atoms joins carbon next to phenyl group and your desired molecule would be minor product.

Offline AromaticAcrobatic

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Re: Could anyone help with this synthesis?
« Reply #2 on: August 23, 2014, 11:54:00 PM »
I agree, the first route would probably work with excess and pyridine as a solvent.
But if you wanted to go an exotic route you could start with toluene then friedel crafts acylation, followed by a reduction to the secondary alcohol, followed by TsCl in pyrdine, followed by a sterically hindered base ( to maximize yield), then anti markov addition of hydration followed HBr. Then Gridnard ad ethanal then water. Then either socl2 in pyridine or HCl in a polar aprotic solvent of your choice.
« Last Edit: August 24, 2014, 12:19:08 AM by AromaticAcrobatic »

Offline quantumnumber

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Re: Could anyone help with this synthesis?
« Reply #3 on: August 24, 2014, 08:17:12 AM »
Thank you very much, it helped me a lot!

Offline zsinger

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Re: Could anyone help with this synthesis?
« Reply #4 on: August 24, 2014, 09:49:16 AM »
Aromatic-
That is too many steps, and would likely suffer in in yields.
   
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Offline AromaticAcrobatic

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Re: Could anyone help with this synthesis?
« Reply #5 on: August 24, 2014, 02:16:30 PM »
Quantum,
Your Welcome, I'm glad this helped.
I must apologize though, as it was late last night when I was looking at this and I forgot the addition of the benzylic Chlorine. To add the benzylic Chlorine after the big sterically hindered base step, add Br2, H20 to the Alkene to get the Halohydrin. Then tmscl in Et3N, then proceed with the rest of the reaction.

Zsinger,
I agree this is a lot of steps but I liked it because we can selectively add/substitute to the alpha Carbon.

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