2,4,6-Trimethylaniline → 1-{6-[(1E)-N-(2,4,6-Trimethylphenyl)ethanimidoyl]pyridin-2-yl}ethan-1-one

2,6-Diacetylpyridine (7.3 g, 44.8 mmol) and 2,4,6-trimethylaniline (5.74 g, 42.55 mmol) were dissolved in 450 ml of toluene. To this solution, 4 Å molecular sieves and a small amount of p-toluenesulphonic acid (0.22 mmol) were added. The mixture was refluxed for 16 hours. After filtration the solvent was removed in vacuo. Several crystallisations from ethanol yielded 3.42 g (28.7%) of monoimine (1). 1H-NMR (CDCl3) δ 8.55 (d, 1H, Py-Hm), 8.11(d, 1H, Py-Hm), 7.92 (t, 1H, Py-Hp), 6.89 (s, 2H, ArH), 2.77(s, 3H, Me), 2.27 (s, 3H, Me), 2.22 (s, 3H, Me), 1.99 (s, 6H, Me). 3. Preparation of 2-[1-(2,4,6-trimethylphenylimino) ethyl]-6-[1-(4-tert-butylphenylimino)ethyl]pyridine (2) Monoimine (1, 2.8 g, 10 mmol) and 4-tert-butylaniline (1.49 g, 10 mmol) were dissolved in 100 ml of toluene. To this solution, 4 Å molecular sieves and a small amount of p-toluenesulphonic acid (0.1 mmol) were added. After standing for 5 days with addition of more 4 Å molecular sieves, the mixture was refluxed for 2 hours. After filtration the solvent was removed in vacuo. The residue was washed with methanol and recrystallised from ethanol. Yield 2.4 g (58%) of mixed diimine (2). 1H-NMR (CDCl3)δ 8.42 (d, 1H, Py-Hm), 8.34 (d, 1H, Py-Hm), 7.86 (t, 1H, Py-Hp), 7.38 (d, 2H, ArH), 6.89 (s, 2H, ArH), 6.78 (d, 2H, ArH), 2.42 (s, 3H, Me), 2.29 (s, 3H, Me), 2.22 (s, 3H, Me), 2.00 (s, 6H, Me), 1.34 (s, 9H, But). 4. Preparation of 2-[1-(2,4, 6-trimethylphenylimino) ethyl]-6-[1-(4-tert-butylphenylimino) ethyl]pyridine iron[II]chloride complex (3) In an inert atmosphere a solution of 1.5 g diimine (2, 3.6 mmol) in 100 ml dichloromethane was added to 420 mg FeCl2 (3.3 mmol) in 150 ml dichloromethane. The mixture was stirred for one week. The developed blue precipitate was isolated by filtration and dried in vacuo. Yield 1.5 g (84%) of iron complex (3). 1H-NMR (Cl2CDCDCl2, broad signals) d 79.3 (1H, Py-Hm), 77.7 (1H, Py-Hm), 27.0 (1H, Py-Hp), 20.7 (3H, Me), 17.3 (6H, Me), 15.0 (2H, ArH), 14.3 (2H, ArH), 1.2 (9H, But), −2.6 (3H, MeC═N), −17.9 (2H, o-ArH), −32.1 (3H, MeC═N). 5. Preparation of 2,6-bis-[1-(2,6-difluorophenylimino) ethyl]pyridine (4) 2,6-Diacetylpyridine (1.76 g, 10.8 mmol) and 2,6-difluoroaniline (2.94 g, 22.8 mmol) were dissolved in 50 ml of toluene. To this solution, 4 Å molecular sieves were added. After standing for 3 days, with addition of more 4 Å molecular sieves the mixture was filtered. The solvent was removed in vacuo. The residue was crystallised from ethanol. Yield of 4: 1 g (24%). 1H-NMR (CDCl3) δ 8.44 (d, 2H, Py-Hm), 7.90 (t, 1H, Py-Hp), 7.05 (m, 2H, ArH) 6.96 (m, 4H, ArH), 2.44 (s, 6H, Me). 19F-NMR (CDCl3) δ −123.6. 6. 2,6-bis-[1-(2,6-difluorophenylimino)ethyl]pyridine iron[II]chloride complex (5) In an inert atmosphere 493 mg diimine (4, 1.27 mmol) was dissolved in 50 ml THF. FeCl2 (162 mg, 1.28 mmol) in 10 ml THF was added. After stirring for 16 hours at room temperature, the solvent was removed in vacuo. Toluene (100 ml) was added. The blue precipitate was isolated by filtration, washed with pentane and dried in vacuo. Isolated 0.5 g (76%) of iron complex 5. 1H-NMR (Cl2CDCDCl2, broad signals) δ 75.5 (2H, Py-Hm), 39.6 (1H, Py-Hp), 15.7 (4H, ArH), −11.6 (2H, ArH), −22.4 (6H, MeC═N). 19F-NMR (Cl2CDCDCl2) δ −70.3. 7. Alternate Preparation of 2,6-bis-[1-(2,6-difluorophenylimino)ethyl]pyridine iron[II]chloride complex (5′) In an inert atmosphere a solution of 60 mg FeCl2 (0.47 mmol) in 0.5 ml ethanol was slowly added to a solution of 260 mg diimine (4, 0.67 mmol) in a solvent mixture of 10 ml toluene and 6 ml pentane. The resulting blue precipitate was isolated by centrifugation, washed three times with toluene and dried in vacuo. Yield 210 mg (87%) of iron complex 5′. 1H-NMR (CD2Cl2, broad signals) δ 76.7 (2H, Py-Hm), 37.6 (1H, Py-Hp), 16.8 (4H, ArH), −10.2 (2H, ArH), −20.3 (6H, MeC═N). 19F-NMR (CD2Cl2) δ −75. 8. Preparation of 2-[1-(1-naphthylimino)ethyl]-6-acetylpyridine (6) 2,6-Diacetylpyridine (5.49 g, 33.6 mmol) and 1-aminonaphthalene (4.8 g, 33.5 mmol) were dissolved in 100 ml of toluene. To this solution molecular sieves (4 Å) were added. After standing for 20 hours at room temperature, the mixture was filtered. The solvent was removed in vacuo. The resulting mixture of 2,6-diacetylpyridine, 2,6-bis-[1-(1-naphthylimino)ethyl]pyridine and 2-[1-(1-naphthylimino)ethyl]-6-acetylpyridine was dissolved in 50 ml THF. The diiminepyridine by-product 2,6-bis-[1-(1-naphthylimino)ethyl]pyridine was removed by selective complexation to a metal halide. FeCl2 (0.79 g , 6.23 mmol) was added in an inert atmosphere. After stirring for 16 hours at room temperature, the solvent was removed in vacuo. Toluene (100 ml) was added to the resulting mixture. The precipitated complex was filtered off over a small layer of silica, yielding a yellow solution. The solvent was removed vacuo. Crystallisation from ethanol yielded 3.25 g of 2-[1-(1-naphthylimino)ethyl]-6-acetylpyridine (6) (33.6%). 1H-NMR (CDCl3) δ 8.65 (d, 1H, Py-Hm), 8.15 (d, 1H, Py-Hm), 7.95 (t, 1H, Py-Hp), 7.87 (d, 1H, ArH), 7.76 (d, 1H, ArH), 7.64 (d, 1H, ArH), 7.4-7.6 (m, 3H, ArH), 6.82 (d, 1H, ArH), 2.79 (s, 3H, Me), 2.38 (s, 3H, Me). 9. Preparation of 2-[1-(1-naphthylimino)ethyl]-6-[1-(4-tert-butylphenylimino)ethyl]pyridine (7) Monoimine (6, 1.25 g, 4.34 mmol) and 4-tert-butylaniline (0.65 g, 4.34 mmol) were dissolved in 50 ml of toluene. To this solution, molecular sieves (4 Å) were added. After standing for 16 hours the mixture was filtered. The solvent was removed in vacuo. The residue was recrystallised from ethanol. Yield 0.44 g (24%) of mixed diimine (7, 96% purity by NMR). 1H-NMR (CDCl3) δ 8.51 (d, 1H, Py-Hm), 8.38 (d, 1H, Py-Hm), 7.91 (t, 1H, Py-Hp), 7.86 (d, 1H, ArH), 7.78 (d, 1H, ArH), 7.63 (d, 1H, ArH), 7.4-7.6 (m, 5H, ArH), 6.8-6.9 (m, 3H, ArH), 2.43 (s, 3H, Me), 2.37 (s, 3H, Me), 1.34 (s, 9H, But). 10. Preparation of 2-[1-(1-naphthylimino)ethyl]-6-[1-(4-tert-butylphenylimino)ethyl]pyridine iron[II]chloride complex (8) In an inert atmosphere, a solution of 440 mg diimine (7, 1.05 mmol) in 5 ml dichloromethane was added to 130 mg FeCl2 (1.03 mmol) in 20 ml dichloromethane. The mixture was stirred for 9 days. Addition of 10 ml pentane yielded a blue precipitate, which was isolated by centrifugation and dried in vacuo. Yield 480 mg (85%) of iron complex (8) 1H-NMR (Cl2CDCDCl2), gave broad signals which were not further assigned. 11. Preparation of 2-[1-(2-tert-butylphenylimino)ethyl]-6-acetylpyridine (9) 2,6-Diacetylpyridine (4.37 g, 26.78 mmol) and 2-tert-butylaniline (4.0 g, 26.8 mmol) were dissolved in 100 ml of toluene. To this solution, molecular sieves (4 Å) were added. After standing for 20 hours at room temperature, the mixture was filtered. The solvent was removed in vacuo.

1. temperatureThe mixture was refluxed for 16 hours
2. filtrationAfter filtration the solvent
3. customwas removed in vacuo
4. customSeveral crystallisations from ethanol

ORD record

ord-d0378c6094f54d789aefe81b64640372

Source dataset

uspto-grants-2006_05

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US07037988B2