[dani]

Hi evreybody, I am synthetisizing two kind of bodipy molecules . In the last step I functionalize with a triethoxysilane (aminoethylt trymethoxy silane or APTES) group the dyes by the following proces (see also the file attached)
 

BODIPY-COOH + APTES + TEA + COMU  BODIPY-CONHCH₂CH₂Si(OEt)₃

The COOH group is linked through an alkyl chain to the meso position of the bodipy.

After the reaction the solvent is removed and the raw material is purified on silica gel by chromatography with petroleumether/AcOEt 50%/50% to 100% AcOEt as eluent.

Simmetric Bodipy (1,3,5,7 methyl 2,6 ethyl substituted     R=Et in the file attached) is an orange solid stable after the purification
Asimettric Bosipy  (1,3,5,7 methyl 2 ethyl substituted   R=H in the file attached)  is not stable and decompose in a dark red brownish insoluble solid the day after the purification and solvent removal. It happens evrey time I try to isolate it. Anyone knows why does this hanppen?

Thank you very much

[wildfyr]

There is no way that ethoxy silane can handle be columned.

You are dreaming if you think A. the silica is dry enough and B. the ethyl acetate is dry enough.

Maybe this could be done under glove box conditions. Any water will oligomerize your silane, and also your silica gel silanols are being functionalized with this very fancy molecule.

[dani]

The yields are variable and depend on hoe fast you run the chromatography , but I have just isolated the simmetric bodipy in 42% yield. The asimmetric one 39% yield but decomposed the next day. This is not the only one trial I made, but their behaviour remain always the same

[dani]

I have discovered that the asimmetric bodipy (actually the raw mixture after solvent removal and before the chormatography) is stable for weeks at room T and air. Another point is that I tried to extract al the amine from the mixture with DCM/water+HCl . Then to the final product I added some amount of silica gel to simulate the chromatography and the next day I found no decomposition. Of course Amine catalyze hydrolisis and binding to silica matrix, but this do not explain the decomposition of the bodipy moiety and most of all the different behaviour of simmetric and asymmetric bodipy (the former is uneffected and is stable even after the chirmatography without work up after the reaction).
So to summarize
- both symmetric and asymmetric bodipy are stable before chormatography (in the raw dry mixture with amines and other compunds that formes during the reaction)
-purification though silica gel starts asymmetric bodipy decomposition , but leaves the symmetric one uneffected
-working up the reaction seems to make the asymmetric boidipy stable after purification through silica gel (but I tried only one time and in small scale)

[rolnor]

I have discovered that the asimmetric bodipy (actually the raw mixture after solvent removal and before the chormatography) is stable for weeks at room T and air. Another point is that I tried to extract al the amine from the mixture with DCM/water+HCl . Then to the final product I added some amount of silica gel to simulate the chromatography and the next day I found no decomposition. Of course Amine catalyze hydrolisis and binding to silica matrix, but this do not explain the decomposition of the bodipy moiety and most of all the different behaviour of simmetric and asymmetric bodipy (the former is uneffected and is stable even after the chirmatography without work up after the reaction).
So to summarize
- both symmetric and asymmetric bodipy are stable before chormatography (in the raw dry mixture with amines and other compunds that formes during the reaction)
-purification though silica gel starts asymmetric bodipy decomposition , but leaves the symmetric one uneffected
-working up the reaction seems to make the asymmetric boidipy stable after purification through silica gel (but I tried only one time and in small scale)

Boron containing compounds are a special world, they can surprice you with good stability towards acids and base