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Ugi NMR Analysis
To monitor the reaction of
by NMR and then to remove excess water. The purpose of removing the water is to see if the addition of the acid
will push back the imine formation to the aldehyde or further the imine formation. This will be compared to Exp048.
(351mg, 2mmol) and separately diluted with 1mL MeOH-d4 then brought up to 2mL mark in a 2mL volumetric flasks. Also measured out
(210uL, 2mmol) diluted in 1mL MeOH-d4 then brought up to 2mL in 2mL volumetric flask. Proton and Carbon NMR were taken of a mixture of the aldehyde and amine. The imine solution is then exposed to some drying agent, in this case 3A sieves and a little MgSO4. The acid is then added and more HMR are taken to monitor the concentration of the aldehyde and imine.
Characterization of Starting Materials
Characterization of PartI - Imine Formation
Characterization of PartII - Addition of Acid
After sieves were added HMR
25minsPartII-D after MgSO4 exposure.
Exp051PartII Kinetics excel
- HMR A,D,H,&K from Part 1 along with aldehyde and amine
- All CMR from Part 1
- HMR Before and after Sieves,B,&D from Part 2 with aldehyde amine and acid
Exp051 Kinetics excel
Using the peak at 9.75 ppm for the aldehyde and the peak at 8.25 ppm for the imine, there is a 47.64% conversion of the aldehyde to imine after 119 min. There is a 13.89% decrease of the amine using the peak at 1.155ppm after 119mins. The reaction did not go to completion but there is a 55% difference in aldehyde/amine concentrations with an excess of amine.
Addition of the Boc-Gly caused the percent imine becomes 34.55% compared to the aldehyde after 25 minutes. Without treatment with 3A sieves, the proportion of aldehyde went from 57% to 96% in 20 min after addition of the acid
. This strongly suggests that the sieves are effective in trapping water and preventing some of the reversal.
The sieves were only used for the last 20 minutes of the 2.5 hour imine reaction. Use from the start of the reaction and letting the reaction go to near completion should more clearly answer the question of whether the reversal to the aldehyde by Boc-Gly can be fully inhibited.
The use of 3A molecular sieves in methanol shows some effect in inhibiting the hydrolysis of an imine by Boc-Gly.
11:00] Prepared 2mmol solutions of piperonal, Boc-Gly-OH and tert-butylamine in MeOH-d4 using 2mL volumetric flasks. Transfered to 1 dram vials.
17:25] Took tert-butylamine HMR - transfered solution back to vial after HMR was taken.
17:35] Took piperonal HMR - transfered solution back to vial after HMR was taken.
18:03] Took Boc-Gly-OH HMR - transfered solution back to vial after HMR was taken.
18:25] Mixed 400uL of aldehyde and 400uL of amine in NMR tube and 500uL of each in a separate 5dram vial, took HMR 051PartI-A
18:31] Took HMR 051PartI-B
18:38] Took CMR 051PartI-C 120scans 5sec relaxation delay
18:55] Took HMR 051PartI-D
19:01] Took CMR 051PartI-E 120scans 5sec relaxation delay
19:18] Took HMR 051PartI-F
19:25] Took CMR 051PartI-G 120scans 5sec relaxation delay
19:49] Took HMR 051PartI-H
19:57] Took HMR 051PartI-I
20:03] Took CMR 051PartI-J 120scans 5sec relaxation delay
20:19] Took HMR 051PartI-K
20:23] The Imine solution in the NMR tube was transfered to a the 5 dram vial that had the extra 1mL of imine solution that had been reacting for the same amount of time. Some 3A sieves were added to 600uL of the imine solution in a separate 5 dram vial, one bead at a time until the bottom of the vial was slightly covered. Sieves had to be reactivated before hand by heating a small amount over a Bunsen burner in a crucible for two minutes - only these sieves were used. After counting there were 16 sieves (about 100 mg) in the vial. Attempted to dry 600uL of imine solution with MgSO4 and filter but lost the solution.
20:40] Used a micropipet and pipetted out 400uL of the imine solution that had been exposed to the sieves and added 400uL of acid solution.
20:46] Took HMR 051Imine after exposure to 3A sieves.
20:57] Took HMR 051PartII-A
21:02] Took HMR 051PartII-B
21:12] Took HMR 051PartII-C
21:14] Imine/acid solution was showing signs of reverting back to the aldehyde. Took solution in NMR tube and transfered it to another clean 5 dram vial with a small amount (>1mg) of MgSO4.
21:18] Pipetted 800uL of the imine/acid solution into the same NMR tube. Noticed some floating debris which was probably MgSO4.
21:20] Took HMR 051PartII-D after exposure to small amount of MgSO4.
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