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Ugi NMR Analysis
To perform the imine reaction of piperonal and tertbutyl amine, remove water with 3A molecular sieves to hault reversal of the imine to the aldehyde. If it is successful, the imine will be used toward a Ugi product.
Made a solution of piperonal(148.1mg, 0.986mmol in 2 ml MeOH, 0.49M) and a solution of tertbutylamine(105uL, 1mmol in 2 ml MeOH, 0.5M). Combined the two solutions in the presence of 66 x 3A molecular sieves(~453mg) with stirring overnight. Took an NMR of the resulting solution. Filtered off crushed molecular sieves to obtain an NMR. Made a solution of Boc-Gly-OH(186.7mg, 1.066mmol in 2 ml MeOH, 0.53M) and added 1mL to the resulting imine solution.
Characterization of Starting Materials
Starting materials were obtained from the same jars and bottle that were used in
No new NMR were taken.
HMR of 69A (after 32hrs)
zero set to t-butyl, not TMS
Addition of Boc-Gly-OH
HMR of 69B (after 1hr)
There is a 2.6% difference between the amine and aldehyde concentrations with an excess of amine(peak 1.155ppm) than aldehyde as the aldehyde (peak 9.8ppm) converts 92% to the imine after 32 hours. However the imine (peak 8.2ppm) is reverted back to the aldehyde in a 76% difference 1 hour after the addition of the acid.
One possibility is that the methanol that was used was wet. After the molecular sieves were filtered off, water could only come from the acid and methanol.
Drying the methanol prior to the experiment should be done and has probably been a direct cause for prior failures.
The imine reverts back to the aldehyde with just 1mL of a 0.5M solution of the acid in a 0.5M solution of imine that was dried in the presence of 3A molecular sieves.
10:05] Prepared (2mL, 1mmol)solutions of piperonal and tertbutylamine in methanol.
10:15] Combined solutions in a 13mL vial with a stir bar and started stirring with a cap that had parafilm to prevent solvent loss.
10:20] Added 66 3Amolecular sieves(~453mg). Sieves were tested for activity by placing a drop of water onto several in the palm of my hand.
11:05] Molecular sieves have been ground up by stir bar.
17:20] Stopped solution spinning. Began to filter off imine solution through a pasteure pipette with glass wool. Then with a new glass pipette and cotton. Performed the cotton filtration twice. The resulting amount of imine solution was used for the next step.
17:40] With a micropipette, took 400uL, put under high vacuum for an NMR(pressure was not obtained). Any amine still present may have evaporated.
17:45] Prepared (2mL, 1mmol) solution of Boc-Gly-OH and added 1mL to the imine solution. Did not stir due to time only shook solution.
18:00] Took dried sample and added approximately 1.5mL of MeOH-d4 to get an HMR of
always take dried samples in CDCl3 if at all possible - this defeats the point of taking samples instead of doing the reaction in methanol-d4
18:10] Obtained HMR of imine solution (69A)
18:40] Took a 500uL sample of imine/acid solution. Put it under high vacuum(pressure was not obtained).
19:00] Removed sample from vacuum and added approx 1.5mL of MeOH-d4 to get HMR of
19:10] Took HMR of imine/acid sample after 1hr
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