Boc is a protecting group for amines, but not for carboxylic acids. Of course, you can react benzoic acid with Boc anhydride to obtain a reactive mixed Bz-Boc anhydride, but it is not a protection, but activation. You can easily obtain an ester with butanol by reacting benzoic acid with BuOH in the presence of a strong acid (say 2-3% of H2SO4), perhaps with a reflux. But again, butyl group os not the best choice as a protecting group (i.e. group that can be easily removed). Why not the simplest methyl group? Well, the choice of protection depends on your synthetic tasks...
Dear Anup,
You could try Mitsunobu reaction using your carboxylic acid derivative, tBuOH, PPh3 and diisopropyl azadicarboxylate which is better than DEAD (less toxic). Now, as mentioned by Igor above you could try others protecting groups (e.g. MeO, Bn,...) which are more stable.
I hope I answered your question.
Regards
Hi there,
I'd strongly recommend the Steglich esterification.
Operationally very simple, no need for strong acid.
http://en.wikipedia.org/wiki/Steglich_esterification
methylation is better way to protect the benzoicacid and further you can convert this ester to alcohol by LAH reduction.....
you could try anhydrous p-toluensulphonic acid as acid catalyst forbenzoicacid esterification with n-butanol. you must to use Dean-Stark trap for removing water.
I used BOC to protect alcohols, you can reduced acid to alcohol (LiAlH4 for example) and then protect with BOC (Boc2O,Mg(ClO4)2 )..[do your reaction].... and unprotect withCeCl3.7H2O/NaI to corresponding alcohol and oxidation to corresponding acid.
If you want the tert-butyl ester then you have to bubble isopropene through an acidic solution of your benzoic acid. This generates the tertiary carbocation which is scavenged by the acid group. This is typically a huge pain as the reagents are horrible. Failing that if you want the n-butyl ester, fisher esterification (with dean stark as mentioned above if you are doing it on a big scale) or benzoyl chloride with butanol and NEt3 at reflux should work.
Dear all,
I want to protect acid part of 4-iodobenzoic acid, so I am looking for the group that can be easily deprotected later. That's why I am thinking about t-butanol. I did same with (Boc)2O and also with DCC,DMAP; but by NMR I'm not sure about the product.
It sounds like you are trying to make a mixed an hydride by treating the COOH with BOc anhydride, this will do nothing productive and you will regenerate starting material and t-BuOH. The same is mostly true for the DCC coupling, while you activate the alcohol it is unlikely that any appreciable amount of t-BuOH will actually couple to to the acid as it is not nucleophilic.
If you want ease of removal why not benzyl ester (Hydrogenolysis removal), even methyl or ethyl esters (Hydrolysis) will prove more productive. Alternatively, start with the 4-iodobenzylalcohol and oxidise up to the COOH after you have done what you need to on the back end.
Method to protect benzoic acid using butanol by esterification reaction in presence of catalytic amount of sulphuric acid . Refer for esterication reaction: Text book of practical Organic Chemistry by A.I.Vogel.
Dear all,
Sorry for mistake in question, its tert-butanol not n-butanol.
Try this one: doi:10.1016/S0040-4039(97)01792-9
BTW: Any isobutene based reactions can be used.
In peptide synthesis, carboxylic groups are protected with t-Bu using isobutylene, it is a standard method. Direct esterification with t-butanol does not work well.
Method to protect benzoic acid using t-Bu by esterification reaction in presence of catalytic amount p-toluen sulphonic acid(anhyrous form)
Hello Laszlo Jicsinszky,
I did the experiment by using the procedure which was mention in the paper which you gave (doi:10.1016/S0040-4039(97)01792-9). I got the product but again yield was very poor. Can you tell me how to do the same reaction properly to get good yield.
Dear Saeideh Hosseini,
Thanks for sending me above attachment. I visited the link which you have attached. It is easy to protect the acids with primary alcohol but i need to protect the same with tertiary alcohol, so I need specific one with t-butyl alcohol. Can you send me any specific one.
Hello Shaban Ahmed Ali Abdel-Raheem,
Thank you for this attachment. Do you have any journal in which such protection has reported i.e protection of benzoic acid with t-butyl alcohol.
Dear all,
I need to deprotect methyl ester [-COOMe] to acid [-COOH] my compound which is insoluble in water. Can anyone suggest the better way to do so?
Thanks & Regards
Anup, for de-protection methyl ester [-COOMe] to acid [-COOH] , you can initially dissolve your sample in THF or MeOH and then add KOH 2M in it and let it go for over night. If you see precipitation of starting material by adding the KOH, you can decrease amount of KOH but in other hands increase KOH's concentration.
Dear Dr Rajabi,
Do I need aqueous KOH or alc. KOH for this purpose. I think, it must be alc. one. It would be a great help, if you may share any reported procedure to do so.
Thanks & Regards
I used aqueous KOH for my case.
please see supp info of : Article Synthesis of MR-49, a deiodinated analog of tetraiodothyroac...
Thank You Sir,
I got the procedure from your link. I will inform you if it's working in my case or not.
Regards
Dear Dr Rajabi,
I tried deprotection of acid with KOH as suggested by you, but it didn't work. May I have any other suggestion.
Regards
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