Exp092-4.JPG

Objective

To investigate the stability of the furan ring of the amide of Boc Glycine and 5-methylfurfurylamine in 50% TFA, in order to investigate the behavior of furan containing Ugi products.

Procedure

In a clean NMR tube a 375 uL of a solution of the amide of Boc Glycine and 5-methylfurfurylamine (~60 mg 0.2 mmol ) in CDCl3 obtained from Exp088 was placed.The solution was diluted by adding another 375 uL of CDCl3. To the NMR tube, then Trifluoroacetic acid (750 uL) was added to make it a 50% in CDCl3. The reaction was monitored by H NMR.

Results

Amide of Boc Glycine and 5MFA.
H NMR
92A
t = 02 min
t = 03 min
t = 08 min
t = 11 min
t = 18 min
t = 21 min
t = 27 min
t = 1 h 39 min
t = 20 h 27 min
t = 23 h 25 min
t = 25 h 28 min
92A1 (after NMR tube broke and sample diluted)
t = 47 h 07 min
t = 54 h 36 min
t = 68 h 07 min

Discussion

  1. Based on the NMRs the removal of the boc group is complete in less than 8min, it is approximately 75% complete with in three minutes of TFA addition at 50% concentration. This can be monitored by disappearance of the t-butyl singlet at 1.44ppm and appearance of a new singlet at 1.6ppm.
  2. The system does not behave the same way as the furan containing Ugi product after 2 day in 10%TFA/CDCl3, where 94% methyl loss was observed in conjunction with the appearance of a pair of doublets at 8.3 and 5.6 ppm (Exp070). Since the NMR tube containing the reaction mixture broke, and a dilution with CDCl3 had to be done, nothing conclusive can be said about the system after 25.5 hours.

Conclusion

The model does not explain the loss of methyl group seen when a Ugi product containing analogous structure is treated with 50% TFA/CDCl3 for 1 day.

Log


2007-04-15

14:00 Transfered 375uL of 88G into an NMR tube, diluted it adding another 375uL of CDCL3, obtained H NMR.
15:13 Added TFA (750uL) to the NMR tube; 92A
15:15 Obtained H NMR of 92A t = 02 min
15:16 Obtained H NMR of 92A t = 03 min
15:21 Obtained H NMR of 92A t = 08 min
15:24 Obtained H NMR of 92A t = 11 min
15:31 Obtained H NMR of 92A t = 18 min
15:34 Obtained H NMR of 92A t = 21 min
15:40 Obtained H NMR of 92A t = 27 min
16:52 Obtained H NMR of 92A t = 1 h 39 min

2007-04-16

11:40 Obtained H NMR of 92A t = 20 h 27 min
14:38 Obtained H NMR of 92A t = 23 h 25 min
16:41 Obtained H NMR of 92A t = 25 h 28 min

2007-04-17

12:30 The NMR tube containing 92A accidentally fell on the floor and shattered. Almost half of the solution got lost. Some of the prduct was recovered and had to be diltued with approximately 300 uL CDCl3 to form 92A1
14:20 Obtained H NMR of 92A1 (t = 47 h 07 min)
21:49 Obtained H NMR of 92A1 (t = 54 h 36 min)

2007-04-18

11:56 Obtained H NMR of 92A1 (t = 68 h 07 min)

Tags

Amide: InChI=1/C13H20N2O4/c1-9-5-6-10(18-9)7-14-11(16)8-15-12(17) 19-13(2,3)4/h5-6H,7-8H2,1-4H3,(H,14,16)(H,15,17)