Hey guys, Im running reaction shown in the scheme
following literature procedure from Tetrahedron Letters 54 (2013) 201–204
whis is basicaly to dissolve the starting material in trifluoroacetic acid to get 0.5M solution and then heat it at 70°C for 16 hours. My problem is that it works great for A (in the scheme) and for others, simpler diamines, while B decomposes into pretty wild mixture. I was able to indentify the product (about 30%) and some impurities: it seems that my product compound and starting material decarboxylates (is that even possible? I thought decarboxylation occurs under basic conditions at much higher temperatures) under the reaction conditions (about 50% of raections mixture) and then some intramolecular cyclization and unidentified produts.
I tried it at lower temperatures (50, RT) and using another procedure (20% TFA in DCM at RT) today but it doesnt seem it is working (see only SM after 5hrs) so I am bit lost at the moment
Im looking for any ideas, does anyone have any useful hints? Could using trifluoroacetanhydride or trifluoracetic acid ester work?
PS: I could oxidize the methyl to carboxylic acid using KMnO4 but I would like to explore all option on cyclizing compound with COOH already present before I try to work on the oxidation