I have bicyclic reaction the start material is 2-aminobenzimidazol with acylation and the solvent which used is DMF > i got clean result after 2 hours but the yield was so low after precipitate at ice water which is difficult to carry out another step .
the complication due to DMF miscible with water so i tried to extract with dichloromethane and dried but also low yield .
SO, is there any modification for another solvent or using catalyst or technique increase yield ?
This question has been asked before in RG and I give one of the answers given to it below:
Ravi Kant Upadhyay
added an answer
February 8, 2015
DMF, and DMC, NMP are aprotic and are toxic, hence there green alternative are to made. Few of its alternative are acetonitrile, methanol, methyl ethyle ketone, 1 butanol, t-butanol , tert-butyl methyl ether, triethylamine and tolune
DMF is a polar aprotic "one which doesn't donate protons in H-bonding" solvent. Other examples of polar aprotic solvents: tetrahydrofuran "THF", dimethylsulfoxide "DMSO", and acetonitrile. When DMF is not suitable, the best to try are THF "has close density to DMF" or DMSO "has close dipole moment to DMF" .
Terpenes and ethyl lactate may also be substitutes for this use of DMF SOLVENT
thank you all for responding and recommendations
Nizar Matar actually I used with THF at room. temperature for 3 days the result is found but the reaction wasn't complete, it appeared 2 clear spots ( product and starting ) i tried to condense it with high temperature but unfortunately the product precipitate through reaction running . and my spots changed and ruined
another polar aprotic solvent like Acetonitrile, Ethyl Acetate, Acetone, or DMSO
Dear Shahd Alansari thank you for your interesting technical question. Apparently acylation reactions of 2-aminobenzimidazol are routinely carried out in DMF. Please have a look e.g. at the following references, which are all available as public full texts:
1. Acyl-2-aminobenzimidazoles: a novel class of neuroprotective agents targeting mGluR5
Article Acyl-2-aminobenzimidazoles: A novel class of neuroprotective...
2. Cyclocondensation of 2-Aminobenzimidazole with Dimedone and Its Arylidene Derivatives
Article Cyclocondensation of 2-Aminobenzimidazole with Dimedone and ...
3. Synthesis and Cyclization of 2-Amino- and 2-Methyl-Substituted 1,3-Diaminobenzimidazolium Salts
https://link.springer.com/content/pdf/10.1007/s10593-014-1627-8.pdf
My suggestion would be to avoid the aqueous work-up. Perhaps you can just evaporate the DMF under vacuum and recrystallize the crude product.
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