July 11, 2020, 04:04:50 AM
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Topic: Two issues  (Read 7115 times)

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Offline Enthalpy

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Re: Two issues
« Reply #15 on: March 27, 2014, 04:25:36 PM »
Calculated densities are extremely inaccurate, from the compounds I needed to know.

Offline Urbanium

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Re: Two issues
« Reply #16 on: April 09, 2014, 09:23:50 AM »
Regards TLC if they are both triflates it is likely they are hydrolysing on contact with the silica-gel giving the triflate precursors, which must be more polar.

In regard to these triflates, I did all the reactions at -30°C and it worked. However, there is a serious issue now. Most of the reactions that involve these triflates gave the products which are viscous oils at room temperature and they are quite unclean (by NMR, which apart from the product shows traces of degraded reagent and little bit of unreacted reactant and some minor impurities).

In the standard isolation/purification procedure, which works on first 4 compounds in the series, I simply add dry diethyl ether and the product precipitates and is easily filtered off. For the rest (unfortunately a majority) of the series adding ether gives an oil (products might actually be liquid at room temperature). However, that oil contains all the impurities mentioned above.

I can't use the flash or column, since these are all triflates. I'm not sure about the reversed phase flash, since it's unaffordable at the moment, and neither about ion-Exchange chromatography, since I have absolutely no practical experience with it. The only other thing I am thinking of is extraction. The reaction is done in DCM, and since the compounds are salt stable in water, I could extract them into aqueous phase. But what to do then? How can I get them from water?

Offline discodermolide

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Re: Two issues
« Reply #17 on: April 25, 2014, 07:25:41 AM »
Evaporate the water with a toluene azeotrope.
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