Exp083_03-29-07.JPG

Objective

To see if steric hinderences allow the formation of the imine supposed to form from crotonaldehyde and tertbutylamine. Also to see one more reaction of a non-aromatic aldehyde. If successful will be used for Ugi reaction.

Procedure

Prepared solutions of crotonaldehyde(83 uL, 1 mmol, 2 mL CDCl3, 0.5 M) and tertbutylamine(105 uL, 1 mmol, 2 mL CDCl3, 0.5 M). Mixed aldehyde and amine solutions together in the presence of 68(x mg) 3A molecular sieves. Allowed imine to form over 3 days. Added 425.7 mg of MgSO4 to imine solution to remove water produced from the reaction then filtered. Prepared a solution of Boc-Gly-OH(182.2 mg, 1.04 mmol, 2 mL CDCl3, 0.52 M) and tert-butylisocyanide(113 uL, 1 mmol, 2 mL CDCl3, 0.5 M) in 2 mL volumetric flasks. Added the two solutions in a 5mL volumetric flask shook well and then added to imine solution.

Results

Characterization of Starting Materials

Crotonaldehyde
Tertbutylamine
Boc-Gly-OH
tertbutylisocyanide

Imine Formation

H NMR 1 hr 083A
H NMR 24 hrs 083B
H NMR 3 days 083C

Addition of Acid and Isocyanide

H NMR 2 hrs 083D

Overlays

ImineRxn overlay
UgiRxn overlay
Exp083 Excel

Discussion

  1. The imine (peak 7.85 ppm) has a 79.16% conversion after three days compared to the aldehyde (peak 9.5 ppm). There is a 2.5% difference between the amine and aldehyde with the amine (peak 1.155 ppm)in access.
  2. After the addition of the acid, the imine decreases to about 35.1% compared to the aldehyde. The percentage of aldehyde increases from 20% to 65% which suggests that there was reversal of the imine to aldehyde. This could be due to the fact that not enough 3A sieves were used in the imine reaction as were used in Exp084. However the disappearance of the amine peak at 1.15 ppm completely suggest that the rest of the amine was used up in some side reaction.
  3. There was no initial NMR taken after the addition of the acid and isocyanide and only the one taken after two hours so no kinetics and not relative concentrations can be determined.
  4. There are multiplets at 6.15ppm, and between 6.8-6.96ppm. There is also a septet at 4.04ppm. Other new peak include 4.38ppm and 4.47ppm. Doublets appear around 2.025ppm and what is possibly a doublet of doublets at 2.055 but this could be a triplet. The acid and the isocyanide peaks overlap but there are also new peaks around 1.42ppm, 1.39ppm, and 1.35ppm. There is still excess imine as can bee seen at 1.2ppm.

Conclusion

There was slight reversal of imine. Ugi as of yet undetermined.

Log

2007-03-29

16:30 Prepared solutions of crotonaldehyde(83 uL, 1 mmol, 2 mL CDCl3, 0.5 M) and tertbutylamine(105 uL, 1 mmol, 2 mL CDCl3, 0.5 M)
17:20 Mixed aldehyde and amine solutions together in a 13 mL vial in the presence of 68(x mg) 3A molecular sieves. Solution was clear.
17:54 Took 200 uL of imine solution and added about 2 mL of CDCl3 to take an initial H NMR
18:38 Took H NMR 1 hr. 083A

2007-03-30

17:52 Took sample of imine solution and without diluting used for HMR
18:10 Took H NMR 24.5hrs 083B

2007-04-02

11:00 Took H NMR of imine solution. 083C
11:45 Added 425.7 mg of MgSO4 to imine solution. Shook well and let sit for several minutes. Filtered solution into new 13 mL vial.
12:12 Prepared a solution of Boc-Gly-OH(182.2 mg, 1.04 mmol, 2 mL CDCl3, 0.52 M) and tert-butylisocyanide(113 uL, 1 mmol, 2 mL CDCl3, 0.5 M) in 2 mL volumetric flasks. Added the two solutions in a 5 mL volumetric flask shook well and then added to imine solution. Solution remained clear.
14:15 Took H NMR 083D

Tags


crotonaldehyde InChI=1/C4H6O/c1-2-3-4-5/h2-4H,1H3/b3-2+
t-butylamine InChI=1/C4H11N/c1-4(2,3)5/h5H2,1-3H3
imine InChI=1/C8H15N/c1-5-6-7-9-8(2,3)4/h5-7H,1-4H3/b6-5+,9-7+
t-butyl isocyanide InChI=1/C5H9N/c1-5(2,3)6-4/h1-3H3