I synthesized piperidine derivative using a heterogeneous catalyst in PEG-200. After completion when i tried to work up the reaction by firstly adding water and then Ethyl acetate, i could not separate the product as it was not soluble in Ethyl acetate. I tried it using methanol also but couldn't get the product. keeping green chemistry principles in view i do not want to use chloroform, can any one please suggest some other solvent which is environment friendly.
Thank you Mr. J.S. Cardoso for your answer, My compound is not soluble in diethyl ether. Can you suggest any other solvent or any solvent combination.
Hey Nayeem, I guess your compound is water soluble and you want to add a second organic layer for proper recovery? Am I correct? Without any more info about M&M or a chemical structure is hard to suggest a proper workaround your problem, however my first thought is maybe MTBE could help so how about trying a green alternative to MTBE such as CPME? You may tackle this in yet another way but it will requiere more work: you may want to start trying a non-Green chemistry solvent(s) to see which throws you better results and then we may find a suitable green chemistry alternatve. Hope this helps
Thank you Mr. Fabio. My compound is not water soluble as when i add water to PEG, i get precipitate. I can recover my product either by adding DMSO or MeOH/CHCl3 mixture, but i don't want to use them as none of them is green.
Thank you Mr. T. Kabir. My compound is not soluble in petroleum ether.
Welcome Nayeem. In that case I strongly suggest a look to Francesca M. Kerton's book Alternative Solvents for Green Chemistry ISBN 978-1-84973-595-7. Check out section 10.2.5. A green substitute for aprotic solvents such as DMSO, DMF and HMPA is piperylene sulfone which has very similar properties to DMSO, completely recyclable and easy to separate. However, just a thought for you to consider: there are several papers in which DMSO has been used as a greener alternative to other solvents and stated as environmentally friendly specially if used in small quantities (see for example 10.1039/C0GC00155D; Green solvents for Chemistry. Ch 6. Green solvents for academic chemistry; Chem. Pharm. Bull. 59 (9) 1089—1093 (2011); ACS Sustainable Chem. Eng., 2013, 1 (12), pp 1609–1618; doi: 10.1021/jf301403f) . Regards, Hope this helps.
According me you can try with mixture of Ethyl acetate and isopropanol( 5% or 10%) which should be enough polar to dissolve your compound, if required you may heat up as well.
Thank you very much Dr. M. Gohain........I am able to dissolve few of my derivatives in Ethyl acetate/Isopropanol, but still i am facing problems in dissolving few of them. Can i try any other combination? i will be highly thankful. These derivatives are soluble in DMSO.
You pls try one thing-just stir your solid compound with 10% NaHCO3 solution and then try to extract with EtOAc or EtOC-IPA. you can even heat up to 50-60oC ,I generally never suggest you to use DMSO
You can even change the work up procedure -just dilute PEG with Ethyl acetate after completion of the reaction, then filter to remove your catalyst-remove Ethyl acetate by distillation and then precipitate out the product by adding water. You can try to recrystallize product from suitable solvent such as IPA, aq IPA etc.
Thank you Dr. M.Gohain....My problem is that the compounds are not soluble in Ethyl acetate or Ethyl acetate/isopropanol mixture. Mixing of 10% NaHCO3 also did not solve the problem. I am forced to use DMSO or MeOH/CHCl3 mixture and the hard choice being that i have to use DMSO. But then the problem of isolating the compounds from DMSO arises. Is there any other combination which you may suggest.
N-Methyl-2-pyrrolidone (NMP)( if available in your lab) also you can try instead of DMSO, but you will face problem of isolation again- one thing you can try just to make basic solvent/solvent system EtOAc/EtOAc-IPA by adding Et3N and then you try, otherwise need details regarding the product then it will be easy to suggest
Hey Nayeem, based on the information collected so far I see a couple possibilities for your issue, let's see. You may use DMSO (or piperylene sulfone as I suggested previously). Reactions conducted in DMSO are often diluted with water to precipitate or phase-separate products, with this in mind you may want to try freeze-drying (lyophilizing) the resulting H2O/DMSO mixture in order to obtain your product. You also may try to use a volatile solvent (ethyl ether may work) that will help in the evaporation of DMSO. Hope it helps.
Thank you Mr. Fabio. The problem arising was the recovery of my compound from DMSO as it is difficult to evaporate by using rotary evaporator. Can you tell me at which temperature will the DMSO/Ethyl ether evaporate.
Hey, I really couldn't say exactly. Under STP conditions no evaporation occurs at 70 degrees Celsius for a mixture 1:1 DMSO and ethyl ether. Is your compound thermically stable?
For piperidine derivative you can use Tetrahydrofuran as a solvent for extraction.
You can also reduce the amount of dmso in your solution by flushing hard Nitrogen gas into it for few hours. I tried 4 hours then I can reduce 50% of the volume..
Alternative solvent other than Ethyl acetate to use in my work-up try Dimethyl formamide (DMF) as product seems to be polar?
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