To check the stability of the furan ring of 5-Methylfurfurylamine in TFA to investigate the behavior of furan containing Ugi products.


A solution of 5-methyl furfurylamine (2229uL, 20mmol) and pure TFA (3mL) in a 3-necked flask, with a condenser and thermometer was heated for about 30 min under N2. A black solid, largely insoluble in CDCl3, was obtained.


111A(MFA+ TFA) [16min]


There was not enough TFA to support a proper reflux, which should never have been able to produce vapour hotter than the boiling point of TFA (72.4C). However, vapour temperatures in excess of 100C were observed.
This reactions should be redone with far less 5-MFA (around 1 mmol) so that a proper reflux of TFA can be carried out.


Heating the trifluoroacetate salt of 5-methylfurfurylamine at high temperatures will convert it into a tar.



15:49 Made-up a solution of 5-methyl furfurylamine (2229uL) and TFA (3mL) in a 50ml 3-necked flask fitted with a reflux condenser and a thermometer that was not immersed in the solution, under nitrogen. See video or pic of set-up(insert). While adding TFA through the neck where the thermometer was placed, the solution fumed and a grey, smoky gas was released. Temp above solution rose to 30C. The obtained solution is 111A
16:05 Obtained H NMR of 111A by dissolving 100uL in 800uL of CDCl3.
16:09 Started heating 111A by turning the variac setting at 100/100.
16:11 Temp above solution 40 degrees C
16:13 Temp above solution 60 degrees C, orange gas released, temperature rose rapidly, refluxing began, Video (stop after first half)
16:15 Temp above solution 105 degrees C
16:17 Temp above solution 129 degrees C, Video
16:19 Temp above solution 130 degrees C,
16:23 Temp above solution 135 degrees C, variac setting changed to 60, Video
16:25 Temp above solution 132 degrees C
16:27 Temp above solution 131 degrees C
16:29 Temp above solution 130 degrees C, thick black tar like substance formed.(111B)
16:30 Switched off the variac and removed a small amount of black gel, which was turning fast into a solid and dissolved in CDCl3 (800uL). The amount obtained using a pipette was less than 100uL (the exact amount could not be found from the pipette since it was thickening as it cooled). The solid was almost insoluble in CDCl3 with most of it floating on top of the solution.
17:10 Obtained H NMR of 111B.


TFA: InChI=1/C2HF3O2/c3-2(4,5)1(6)7/h(H,6,7)