Comments on: Tosylates And Mesylates

By: Jessica Reel

Jessica Reel — Thu, 02 May 2024 15:29:07 +0000

Hi James, thank you for the excellent resource, as always.

A student came to me with a question that makes perfect sense, but I don’t have the level of background knowledge to explain. Given that one of the products of reacting an alcohol R-OH with TsCl is Cl- (chloride anion), would that not be a strong enough nucleophile to immediately displace the OTs group in an SN2/SN1 type of reaction, since OTs is such a good leaving group? How is it possible that we can isolate the tosylate without this happening?

Thank you for any answer!

By: dave t

dave t — Tue, 09 Nov 2021 19:15:08 +0000

There is about 1.2 equ of Tosyl chloride, in pyridine / DMAP. The product is a pivalic acid methyl ester derivative (so more ‘Tosylate’ than other molecule if you see what I mean). The chromatography is on silica, with ethyl acetate / hexane as eluent. I have tried the use of finely devided filter paper to consume the excess tosyl chloride and this seems a promising pathway, prior to chromatography.

By: James Ashenhurst

James Ashenhurst — Tue, 09 Nov 2021 18:22:52 +0000

In reply to dave t. How much excess TsCl did you add? What's the molecule and what kind of solvent system are you using? Cutting your solvent system with a little bit of benzene / toluene will likely help with separation of aromatic groups.

By: dave t

dave t — Sun, 07 Nov 2021 10:44:15 +0000

what is the best way to remove excess tosyl chloride from the reaction mixture. My tosylated product moves at about the same rate as tosyl choride on chromatography.

By: James Ashenhurst

James Ashenhurst — Tue, 02 Jun 2020 15:29:14 +0000

In reply to Bhavana Uppalapati. In real life, substitution reactions on secondary carbons can be tough. What's your substrate and nucleophile? If there's any steric hindrance, and if the nucleophile is at all basic, it will be tough to avoid elimination as a significant byproduct.

By: Bhavana Uppalapati

Bhavana Uppalapati — Tue, 02 Jun 2020 02:18:55 +0000

Hello, I had a question about tosylates and mesylates ability to participate in substitution and elimination reactions. I have a secondary mesylate/tosylate that I prepared from the corresponding secondary alcohol. On the adjacent carbon I have a proton that has been known to be abstracted in previous reactions. How could I predict the propensity for an SN2 vs E2 reaction? Does this depend entirely on the list you covered: i.e substrate, solvent, temperature, nucleophile? Could you direct me to some literature possibly? I was not able to find anything that helped.

Thanks in advance.

By: James Ashenhurst

James Ashenhurst — Tue, 17 Mar 2020 16:32:19 +0000

In reply to zahra. Water is a poor solvent, as it will hydrolyze the tosyl chloride. I would find a non-polar, non-nucleophilic solvent that your substrate is soluble in, such as a chlorinated solvent or an ether, and use that.

By: James Ashenhurst

James Ashenhurst — Tue, 17 Mar 2020 01:58:56 +0000

In reply to Ju. See the new "references" section at the bottom! :-)

By: zahra

zahra — Mon, 16 Mar 2020 05:20:50 +0000

Qestion,
Thanks for your text that is very useful. I want to know that tosylation alcohol can be carried out in water?if not, which solvent are better?

By: Ju

Ju — Tue, 14 Jan 2020 18:54:25 +0000

Hello.
Could you tell me, please, what are the references for this all information?
Thank you!