[crawlingmcedge]

I'm working on a project involving a number of glucose derived amino-HCl salts that I have synthesized and want to put in a few examples of iminium catalysis for my thesis.

The problem is that the salts have awful solubility properties dissolving in pretty much methanol, water, and dmso. It might dissolve in pyridine, but I haven't really tried it out. The real kicker is that they decompose/rearrange in neutral/basic conditions as well, so they have to be in acidic conditions.

I've tried a micheal addition on trans-cinnamaldehyde in methanol, but I ended up with methoxy addition to the aldehyde, probably from the HCl on the amine.

I'm looking for an iminium catalyzed reaction that is also not acid catalyzed, or at the very least significantly less so than the iminium.

[pgk]

Schiff bases cannot easily be formed from carbonyl compounds and amine salts due to the participation of the amine electron pair in the salt structure. So, try transimination of the glusosamine salt with benzophenone imine. This reaction occurs through amine/imine salt exchange and can be effectuated at room temperature. Furthermore, self-Schiff base formation of the glucosamine is avoided that way and thus, it will probably work.
A mild and efficient route to Schiff base derivatives of amino acids, J. Org. Chem., (1982), 47(13), 2663-2666, DOI: 10.1021/jo00134a030
https://pubs.acs.org/doi/abs/10.1021/jo00134a030?journalCode=joceah

[clarkstill]

You can use the HCl salt directly - as far as I'm aware the Macmillan imidazolidinones are always used as the HX salts, since the formation of the iminium species is acid-catalysed.

If you just need any old reaction to test your catalyst, there are a bunch on the aldrich website:

https://www.sigmaaldrich.com/chemistry/chemical-synthesis/technology-spotlights/organocatalyst.html

It looks like the Diels-Alder is carried out in MeOH/H2O so should be a good bet for your solubility issues.

[crawlingmcedge]

You can use the HCl salt directly - as far as I'm aware the Macmillan imidazolidinones are always used as the HX salts, since the formation of the iminium species is acid-catalysed.

If you just need any old reaction to test your catalyst, there are a bunch on the aldrich website:

https://www.sigmaaldrich.com/chemistry/chemical-synthesis/technology-spotlights/organocatalyst.html

It looks like the Diels-Alder is carried out in MeOH/H2O so should be a good bet for your solubility issues.

I really dont care what reaction it is. It's not the main part of my thesis and its just as an aside.

The methanol is an issue though, it just forms methoxy acetal on cinnamaldehyde, which is almost certainly going to be even worse when I have to put it in an acidic solution. I'll try in minimal amounts.

I'm looking for something that is almost completely water soluble.