Sciencemadness Discussion Board

Cant get 2-Chlorophenyl cyclopentyl ketone from grignard reaction

RabbitTy - 23-10-2019 at 02:56

Im synthesising 2-Chlorophenyl cyclopentyl ketone from Cyclopentyl magnesium bromide and o-Chlorobenzonitrile.Follow the ways of ZEALOT and US3254124 and Chen L, Gong Y, Salter R. Synthesis of carbon‐14 labeled ketamine and norketamine[J]. Journal of Labelled Compounds and Radiopharmaceuticals, 2018, 61(11): 864-868.None of them can get the produt.I distilled tetrahydrofuran with Na as the solvent.Grignard reagent was bought,1M in THF. Cool the gringnard reagent in THF to 0℃，the the nitrile added dropwise.Monitor the reaction by TLC.Finally hydrolyze with NH4Cl and 6M HCl. TLC shows several spots that I cant identify product.
Has anyone ever done this experiment, can you tell me important notes and specific actions. Many thanks

Cactuar - 23-10-2019 at 10:40

Still no luck eh? 6M for hydrolysis is overkill. 1M should be enough, do it cold.

Can you show us the TLC and tell us what solvent system you use? Can you show us some pictures from the reaction?

RabbitTy - 24-10-2019 at 21:09

Quote: Originally posted by Cactuar  
Still no luck eh? 6M for hydrolysis is overkill. 1M should be enough, do it cold.

Can you show us the TLC and tell us what solvent system you use? Can you show us some pictures from the reaction?



I use THF as solvent and the grignard are also dissolve in THF,1M/L.
TLC shows as the uploaded file.There are many by-products however I have
to do it in large scale.It baffled me a lot.

Attachment: phpHb9swm (54kB)
This file has been downloaded 434 times

[Edited on 25-10-2019 by RabbitTy]

Cactuar - 25-10-2019 at 00:09

Yes, that looks quite similar to the reaction I posted in your other thread. If you're doing this on a large scale then just distill the product. Any remaining nitrile will come over first with your desired ketone at around 100-130C.

Or just do a normal work-up, dry, evaporate and dissolve the residue in some pet. ether and flash it through a small silica plug with minimal amount of EtOAc. This wont remove the nitrile if there's any left but if you're continuing with the ketamin synthesis it wont really matter. The nitrile will not brominate and the formed a-bromoketone (well the one that I made with 3'-methylphenyl) will crystallize upon the addition of a little methanol.

RabbitTy - 27-10-2019 at 17:58

Quote: Originally posted by Cactuar  
Yes, that looks quite similar to the reaction I posted in your other thread. If you're doing this on a large scale then just distill the product. Any remaining nitrile will come over first with your desired ketone at around 100-130C.

Or just do a normal work-up, dry, evaporate and dissolve the residue in some pet. ether and flash it through a small silica plug with minimal amount of EtOAc. This wont remove the nitrile if there's any left but if you're continuing with the ketamin synthesis it wont really matter. The nitrile will not brominate and the formed a-bromoketone (well the one that I made with 3'-methylphenyl) will crystallize upon the addition of a little methanol.


Thanks a lot!

Cactuar - 28-10-2019 at 10:31

Quote: Originally posted by Cactuar  
... your desired ketone at around 100-130C.


I forgot to mention that this is under vacuum obviously. Good luck and keep us updated! I'd love to see some pictures of the procedure.

RabbitTy - 29-10-2019 at 18:25

Quote: Originally posted by Cactuar  
Quote: Originally posted by Cactuar  
... your desired ketone at around 100-130C.


I forgot to mention that this is under vacuum obviously. Good luck and keep us updated! I'd love to see some pictures of the procedure.


Hi~I changed my route~weinreb ketone synthesis were uesd~Now i can get ketone with good yield~keep u updated