I've never worked with it but all my life I work with insoluble compounds. 🙈

General rules of thumbs:

1. Try to dilute it several times by smaller dilution steps this way the concentration of DMSO in each intermediate solution will be higher which will definitely help. If you dilute it in a few steps, start with water only (due to absorbed CO2 it has lower pH which will help to dissolve amin).

2. Some compounds require higher temperature and sonication.

3. Start with much lower concentration of stock. This will make it easier to dilute and also concentration of DMSO in final solution will be higher, which helps again.

4. Some compounds require certain additives. E.g. even 1-5% DMSO can make a huge difference. If you work with living cells, you have to test how far and for how long you can go (you can start with 1% DMSO). Some CuAAC require some organic cosolvent (I saw also tBuOH).

5. Mixture of several solvents works often much better than each solvent separately.

6. You can use other catalysts for CuAAC with better water solubility.

7. Use different dipolar aprotic solvent for stock. Or better a mixture of them. Try N-Methyl-2-pyrrolidone, povidone with low Mr, maybe even DMPU, DMI, DMF...

Good luck and don't give up! Ultimately I was able to dissolve almost all compounds which seems at first to be insoluble.

Try a 20mM stock instead and use 10ul or try 10% DMSO as reaction medium where you dilute your stock into, or try less concentrate PBS.

Alternatively, THPTA has a higher water solubility: https://www.iris-biotech.de/de/blog/click-chemistry-in-aqueous-solution/ (and references therein)

Change the ratio and try again and observe the result

if still not completely dissolved try to change the solvent.

More alternatives to TBTA for aqueous systems here:

Article A Hitchhiker’s Guide to Click-Chemistry with Nucleic Acids

Not directly dilute with a lot of liquid, because the more gap of concentrations will salt out your compound.

You can try small amount of the dilutions, and use more times of dilution to get the final concentration that you want.

Try to change the solvent,if it's not done please change the ratio cause most of the cases huge gap ratio creat this kind of problem.