Amination of 3,5-di-tert-butylcatechol; secondary amine
SyntheticPage 389
DOI:
10.1039/SP389
Submitted Mar 09, 2010, published Mar 19, 2010
Chemicals Used
2,2´-diamino-6,6´-dimethylbiphenyl
3,5-di-tert-butylcatechol
hexane (not dried)
acetic acid (glacial)
ethanol
Procedure
A 250 ml round bottomed flask with stirrer bar was charged with 2,2´-diamino-6,6´-dimethylbiphenyl (2.12 g, 10.0 mmol) and 3,5-di-tert-butylcatechol (4.44 g, 20.0 mmol) and hexane (100 ml). The mixture was stirred for 20 min, during which time the solution turned pale green/brown. Glacial acetic acid (0.5 ml) was added and the solution was stirred for 24 h, during which time it turned dark brown. Volatiles were removed under reduced pressure to yield a brown foamy solid. Analyses showed this to be the desired product (6.08 g, 98 % yield) with no 1H NMR detectable impurities. Recrystallisation from methanol gave a white crystalline solid. Volatiles were removed from the supernatant in vacuo and the residue recrystallised from ethanol. Yield from crystallisation 70-80%
Author's Comments
The standard catalyst for this reaction is triethylamine, but this gave a yield of only 30% here. For aromatic amines in our hands this additive rarely effects an improvement in conversion compared with no "catalyst" although it does seem that it can lead to some improvement for aliphatic amines. Acetic acid promotes the reaction in the example here.
Data
1H NMR 300 MHz (CDCl3) d ppm 7.21 (d, 2H, 4JHH = 2 Hz), 7.14 (t, 2H, 3JHH = 8 Hz), 6.94 (d, 2H, 4JHH = 2 Hz), 6.89 (d, 2H, 3JHH = 8 Hz), 6.47 (d, 2H, 3JHH = 8 Hz), 6.41 (s, 2H), 4.85 (s, 2H), 2.16 (s, 6H), 1.42 (s, 18H), 1.25 (s, 18H).
13C{
1H} NMR 75 MHz (CDCl
3) d ppm 149.5, 144.9, 142.2, 137.7, 135.3, 129.0, 127.5, 122.6, 122.1, 121.8, 121.6, 111.8, 34.9, 34.2, 31.5, 29.4, 19.7.
Lead Reference
P. N. O’Shaughnessy, P. D. Knight, C. Morton, K. M. Gillespie, P. Scott, Chem. Comm., 2003, 1770.
Other References
H. Chun, C. N. Verani, P. Chaudhuri, E. Bothe, E. Bill, T. Weyhermüller and K. Wieghardt, Inorg. Chem., 2001, 40, 4157; L. A. Maslovskaya, D. A. Petrikevich, V. A. Timoshchuk and O. I. Shadyro, Russ. J. Gen. Chem., 1996, 66, 1842; K. Key and F. Lober, Ger. Pat., 1119297, 1959 to Bayer
Supplementary Information
Optically pure diamine may also be used in this reaction, and no racemication was observed. Crystallisation of the enantiomerically pure material usually requires further crops to keep up the chemical yield.
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Keywords: amination, amines, aromatics/arenes, radical, substitution
