Tosyl chloride (TsCl) is usually used as an activating group for primary alcohols. Due to its relatively large volume and the lower reactivity of secondary and tertiary alcohols, it usually doesn't come into them, being selective to primary alcohols in most of the cases. The -OTs group formed is a good leaving group for substitution reactions. So, using this reagent, it is easier to change functionalities, for example -OH for -N3, -OH for -NHR or -NR2.
Theoretically it is possible to use this group as a protective group also, recovering the -OH treating with NaOH. But I have never seen this use since there are many better protecting groups for alcohols available.
The introduction of Ts in the alcohol follows a similar mechanism than any usual ester formation between an alcohol and a acid chloride, but in this case is not a carboxilic acid, it is a sulfonic acid. For the substitution, a SN2 mechanism occurs, leaving the p-toluensulfonic acid anion.
I have come across a reaction of Aniline + Methylformide + tosyl chloride to give an imide. Here tosyl chloride is used in almost equimolar ratios to that of aniline. what is the role of tosyl chloride here ?
That's an interesting reaction.... Could specify the product you obtain (Ph-N=CH-NH-CH3?) and the reaction recipe? (i.e.: you had everything together or two compounds first and after some time the other, solvent, temperature, inert atmosphere, later work-up...) ... that would help to clarify the possible mechanism.
Sorry sir i can't give you whole detail's about reaction. Can you suggest me any further reaction?
Rubeena Mubeen---- Tosyl chloride is good for protection. & you can remove it as iodine by deprotection. and iodine is very good leaving group......... reply
Mr. Alejandro the product you have predicted is right and regarding the recipe aniline and tosyl chloride are added together (no solvent used)and then methyl formide (7-8 moles) is added . After the completion of reaction, it is basified to obtain the product.
Ok, so, what seems to be happening is that the aniline is attacking (nucleophilic attack) to the carbonyl group in the methylformamide giving an alcohol and, after dehydration, it forms the imide (what is favoured due to the conjugation with the aromatic ring). Nevertheless, the aniline is not a nucleophile as strong as other primary amines due to the conjugation of the lone electron pair with the aromatic ring... so I guess that is here where the tosyl group comes into play. In the first step you add tosyl chloride to the aniline, and that would form the corresponding sulfonamide, enhancing the nucleophile activity of this nitrogen that now is able to attack the carbonyl group to form the imide (with the formation of p-toluen sulfonic acid as by-product instead of water).
I'm not 100% sure, but I think that is the role of the tosyl chloride in this reaction. It isn't the typical use of this reagent, but is a quite nice application.
I dont believe that the nitrogen of aniline get a higher nucleophilicty in the corresponding sulfonamide, instead it is probably the HCl formed that catalyses the reaction when the proton attach to the oxygen in the formamide. The rest of the mechanism seems plausible to me. Cheers
Alejandro Diaz ..your comment "The -OTs group formed is a good leaving group for substitution reactions. So, using this reagent, it is easier to change functionalities, for example -OH for -N3, -OH for -NHR or -NR2."...how would you suggest i treat a tosylated primary alcohol with a function -N3 so as to end up with a cyanuric product....maybe a reference or method would be appreciated.
The role and mechanism of action of tosyl chloride in organic synthesis as a better leaving group. You can prepare alkyl iodide using tosylate.
- Badges
- Science topic
- Similar topics
- Agricultural Science
- Agronomy