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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: AllylicAzideUMN on January 17, 2018, 07:54:43 PM

Title: Tips for reacting an insoluble solid
Post by: AllylicAzideUMN on January 17, 2018, 07:54:43 PM
As part of my research at the University of Minnesota, I am trying to carry out a condensation reaction between sulfamide (O=S(=O)(N)N) and a 1,2-diketone in the presence of an acid catalyst (HCl, p-Tosic acid, or camphorsulfonic acid), but I am observing absolutely no conversion. I suspect this is because the diketone is very insoluble in the alcoholic solvents I am using (which sequester the liberated water and favor products), even at temperatures greater than 170 oC. Unfortunately, the diketone is insoluble in most organic solvents besides a few in which it is just barely soluble (~1 mg/mL in DMSO). What are some tips I could try to increase the diketone's solubility, or other ideas to facilitate this condensation reaction? 
Title: Re: Tips for reacting an insoluble solid
Post by: zarhym on January 17, 2018, 08:40:12 PM
How about neat reaction?
Sulfamide melts at 93°C.
It can be both reagent and solvent for your reaction.
Title: Re: Tips for reacting an insoluble solid
Post by: wildfyr on January 17, 2018, 09:17:57 PM
I like the neat reaction idea. Also, perhaps some experimentation with phase transfer agents could help? Perhaps look at naphthalene based surfactants?

Or, could you get some greasy sidegroups onto your diketone to help it get into solution?
Title: Re: Tips for reacting an insoluble solid
Post by: kriggy on January 18, 2018, 03:04:27 AM
I think you would require high temperature for this because the SO2 group is electron withdrawing. Try some glyme or anything high boiling
Title: Re: Tips for reacting an insoluble solid
Post by: zarhym on January 18, 2018, 07:35:00 AM
Here are some suggestions I found in literature.

1)  10.1002/adfm.201700986

Your starting material was used in suzuki reaction in this literature.
THF was used as the solvent. The yield was 77%.
It looks like your SM should have good solubility in THF.

2) Karischin; Fedorenko - Ukrainskii Khimicheskii Zhurnal (Russian Edition), 1955, vol. 21, p. 373,375, Chem.Abstr., 1955, p. 14722

In this Russian paper, your SM was reacted with various diamines. This kind of condensation reaction was done in acetic acid. Maybe you can also try that.

I also find many reaction using acetic acid as the solvent. It looks like a promising solvent to me.

3) Solvent-Free Condensation Reactions To Synthesize Five-Membered Heterocycles Containing the Sulfamide Fragment (link:   https://www.thieme-connect.de/DOI/DOI?10.1055/s-0035-1561371)

I see many reactions between diketones and sulfamide to synthesis thiadiazoledioxide. It should be a promising route even SO2 group is electron withdrawing.
I highly recommend this literature (link above).  You may repeat the procedure and use the acid mentioned in this literature.

Good Luck.