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Topic: t-butyl group as a coupling partner in Pd-catalysed reactions  (Read 6238 times)

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Offline reflux

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Are there currently any good methods for coupling a t-butyl group to an aryl group via Kumada coupling or any other metal catalysed coupling reaction?  Is it possible to achieve coupling without beta-hydride elimination and/or rearrangement of the t-butyl coupling partner?

Example:  tBu-MgBr + PhOTf + Pd catalyst -->   tBu-Ph

Offline opsomath

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Re: t-butyl group as a coupling partner in Pd-catalysed reactions
« Reply #1 on: July 21, 2011, 10:07:34 AM »
http://pubs.acs.org/doi/abs/10.1021/ja202769t

Seems to do what you want. Need weird ligand though.

Offline reflux

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Re: t-butyl group as a coupling partner in Pd-catalysed reactions
« Reply #2 on: July 21, 2011, 10:39:27 AM »
Thanks opsomath!

I'm not sure how I missed this paper.  Apparently you can buy the NHC ligand from Strem.

Offline OC pro

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Re: t-butyl group as a coupling partner in Pd-catalysed reactions
« Reply #3 on: July 22, 2011, 12:21:57 PM »
Apparently you can buy the NHC ligand from Strem.

Very simple to do on your own and a nice training though... ;D

Offline g-bones

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Re: t-butyl group as a coupling partner in Pd-catalysed reactions
« Reply #4 on: July 22, 2011, 08:02:04 PM »
is this just a mental exercise or are you trying to make that? if so, how about FC alkylation?

Offline zolarpwr

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Re: t-butyl group as a coupling partner in Pd-catalysed reactions
« Reply #5 on: July 26, 2011, 07:41:50 PM »
Kumada couplings are more prone to beta-H eliminations because of the strong basicity of the Grignard reagent. The Negishi or Suzuki route may be preferable. There are also more literature examples of unusual reactions with boronic acids or alkylzinc reagents, tons of ligands available, and more cases of sucess with aryl triflates.

You can also try Ni, which has much less tendency to eliminate than Pd. Not as general, though.

Offline reflux

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Re: t-butyl group as a coupling partner in Pd-catalysed reactions
« Reply #6 on: July 28, 2011, 01:35:37 PM »
Thanks all.  Lots of good options.  Turns out the Kumada conditions work well in our system (which is a naphthol derivative). We did try a Friedel-Crafts alkylation awhile back and it led to a mixture of regioisomers and polyalkylation byproducts.

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