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17.9 (Pho–CH3), 16.4 (NvC(CH3)).26a (See Fig. S6†) MS (ESI): (CAlkyl), 31.5 (CAlkyl), 31.3 (CAlkyl), 25.7 (CAlkyl), 25.6 (CAlkyl), 22.6
m/z 398.2 [M + H]+.
(CAlkyl), 16.1 (CAlkyl), 14.1 (CAlkyl). (See Fig. S10†) C,H,N ana-
2-Acetyl-6-{1-[(2,6-diethylphenyl)imino]ethyl}pyridine (3c). lysis: theoretical [C31H39N3] = C 82.07 H 8.67, N 9.26; found C
1H NMR (400 MHz, CDCl3; δ, ppm) 8.57 (d, 1H, pym–H), 8.14 81.22, H 8.49, N 9.19. MS (ESI): m/z 454.3 [M + H]+.
(d, 1H, pym–H), 7.95 (t, 1H, pyp–H), 7.13 (d, 2H, Phm–H), 7.05
2-Acetyl-6-{1-[(2,6-dimethyl,4-hydroxyphenyl)imino]ethyl}
(t, 1H, Php–H), 2.79 (s, 3H, OvC(CH3)), 2.37 (m, 4H, CH2), pyridine (3g). In the crude, the following peaks could be distin-
2.25 (s, 3H, NvC(CH3)), 1.14 (t, 6H, CH3). 2,6-Bis{1-[(2,6-di- guished by 1H NMR (400 MHz, CDCl3; δ, ppm) 8.54 (d, 1H,
ethylphenyl)imino]ethyl}pyridine (4c): 1H NMR (400 MHz, pym–H), 8.13 (d, 1H, pym–H), 7.93 (t, 1H, pyp–H), 6.58 (s, 2H,
CDCl3; δ, ppm) 8.48 (d, 2H, pym–H), 7.93 (t, 1H, pyp–H), 7.13 Phm–H), 2.79 (s, 3H, OvC(CH3)), 2.24 (s, 3H, NvC(CH3)), 1.99
(d, 4H, Phm–H), 7.04 (t, 2H, Php–H), 2.40 (m, 8H, CH2), 2.26 (s, (s, 6H, Phm–CH3), Ph–OH was not observed in the crude. 2,6-Bis
6H, NvC(CH3)), 1.15 (t, 12H, CH3). 13C{1H} NMR (100 MHz, {1-[(2,6-dimethyl,4-hydroxyphenyl)imino]ethyl}pyridine
(4g):
CDCl3; δ, ppm) 166.9 (Cq), 155.1 (Cq), 147.8 (Cq), 136.9 (Cq), 1H NMR (400 MHz, (CD3)2CO; δ, ppm) 8.53 (d, 2H, pym–H),
131.2 (Ar–CH), 125.9 (Ar–CH), 123.3 (Ar–CH), 122.2 (Ar–CH), 8.09 (t, 1H, pyp–H), 7.83 (s, 2H, Php–OH), 6.66 (s, 4H, Phm–H),
24.6 (Ar–CH2–CH3), 16.8 (NvC(CH3)), 13.8 (Ar–CH2–CH3).34 2.28 (s, 6H, NvC(CH3)), 2.00 (s, 12H, Pho–CH3). 13C{1H} NMR
(See Fig. S7†) MS (ESI): m/z 426.3 [M + H]+.
(100 MHz, (CD3)2CO; δ, ppm) 169.2 (Cq), 157.1 (Cq), 154.7 (Cq),
2-Acetyl-6-{1-[(2,6-diisopropylphenyl)imino]ethyl}pyridine 143.1 (Cq), 138.6 (Cq), 127.8 (Ar–CH), 123.5 (Ar–CH), 116.2 (Ar–
1
(3d). H NMR (400 MHz, CDCl3; δ, ppm) 8.57 (d, 1H, pym–H), CH), 18.9 (Ar–CH3), 17.3 (NvC(CH3)). (See Fig. S11†) MS (ESI):
8.15 (d, 1H, pym–H), 7.96 (t, 1H, pyp–H), 7.19 (d, 2H, Phm–H), m/z 402.2 [M + H]+.
i
7.12 (t, 1H, Php–H), 2.80 (s, 3H, OvC(CH3)), 2.73 (m, 2H, Pr–
2-Acetyl-6-{1-[(4-methoxyphenyl)imino]ethyl}pyridine (3h).
CH), 2.27 (s, 3H, NvC(CH3)), 1.16 (brm, 12H, Pr–CH3).35 MS In the crude, the following peaks could be distinguished by 1H
(ESI): m/z 323.2 [M + H]+. 2,6-Bis{1-[(2,6-diisopropylphenyl) NMR (400 MHz, CDCl3; δ, ppm) 8.46 (d, 1H, pym–H), 8.10 (d,
imino]ethyl}pyridine (4d): the following peaks could be clearly 1H, pym–H), 7.91 (t, 1H, pyp–H) 2.78 (s, 3H, OvC(CH3)), 2.32
distinguished by H NMR (400 MHz, CDCl3; δ, ppm) 8.50 (d, (s, 3H, NvC(CH3)). 2,6-Bis{1-[(4-methoxyphenyl)imino]ethyl}
2H, pym–H), 2.28 (s, 6H, NvC(CH3)), 1.28 (d, 6H, Pr–CH3). pyridine (4h): H NMR (400 MHz, CDCl3; δ, ppm) 8.33 (d, 2H,
The remainder overlap with those of 3d.36 (See Fig. S8†).
pym–H), 7.85 (t, 1H, pyp–H), 6.96–6.81 (m, 8H, Ph–H), 3.84 (s,
i
1
i
1
2-Acetyl-6-{1-[(2-isopropylphenyl)imino]ethyl}pyridine (3e). 6H, O–CH3), 2.44 (s, 6H, NvC(CH3)). Due to fluxionality in solu-
The following peaks could be clearly distinguished by 1H NMR tion/multiple orientations of the imino-aryl/phenoxy groups, a
(400 MHz, CDCl3; δ, ppm) 8.56 (d, 1H, pym–H), 8.16 (d, 1H, higher number of peaks in the 13C are observed than would be
pym–H), 7.95 (t, 1H, pyp–H), 2.84 (s, 3H, OvC(CH3)), 2.44 (s, expected for a symmetrical ligand, the ranges are consistent with
3H, NvC(CH3)), 1.24 (d, 6H, CH3).35 2,6-Bis{1-[(2-isopropyl- literature reports:38 13C{1H} NMR (100 MHz, CDCl3; δ, ppm)
phenyl)imino]ethyl}pyridine (4e): 1H NMR (400 MHz, CDCl3; 167.5 (CAryl), 166.7 (CAryl), 156.5 (CAryl), 156.2 (CAryl), 152.8
δ, ppm) 8.41 (d, 2H, pym–H), 7.90 (t, 1H, pyp–H), 7.33 (d, 2H, (CAryl), 152.7 (CAryl), 152.3 (CAryl), 144.1 (CAryl), 139.8 (CAryl),
Pho–H), 7.20 (t, 2H, Phm–H), 7.12 (t, 2H, Php–H), 6.65 (d, 2H, 137.9 (CAryl), 137.1 (CAryl), 124.8 (CAryl), 124.7 (CAryl), 122.3
i
Phm–H), 3.02 (m, 2H, Pr–CH), 2.39 (s, 6H, NvC(CH3)), 1.20 (CAryl), 120.1 (CAryl), 116.5 (CAryl), 114.8 (CAryl), 114.2 (CAryl),
(brd, 12H, CH3). 13C{1H} NMR (100 MHz, CDCl3; δ, ppm) 166.5 55.9 (O–CH3), 55.5 (O–CH3), 25.7 (CAlkyl), 25.5 (CAlkyl), 16.3
(Cq), 155.5 (Cq), 148.7 (Cq), 138.2 (Cq), 136.8 (Ar–CH), 126.2 (CAlkyl), 16.1 (CAlkyl). (See Fig. S12†). MS (ESI): m/z 374.2
(Ar–CH), 125.7 (Ar–CH), 124.0 (Ar–CH), 122.2 (Ar–CH), 118.4 [M + H]+.
(Ar–CH), 28.5 (iPr–CH), 22.9 (Ar–CH-(CH3)2), 16.5 (NvC
(CH3)).34,37 (See Fig. S9†) MS (ESI): m/z 398.2 [M + H]+.
2-Acetyl-6-{1-[(4-amylphenyl)imino]ethyl}pyridine (3f). In
the crude, the following peaks could be distinguished by 1H
No reaction was observed for 1 and 2i (see Fig. S13†).
General procedure for the scaled-up mechanochemical reaction
of 1 with 2a or 2h
NMR (400 MHz, CDCl3; δ, ppm) 8.49 (d, 1H, pym–H), 8.12 (d, In a tungsten carbide vessel, diacetylpyridine 1 0.006 mol
1H, pym–H), 2.80 (s, 3H, OvC(CH3)). 2,6-Bis{1-[(4-amylphenyl) (1.0 g) was mixed with 0.0182 mol (2.20 g) 2,6-dimethylaniline
1
imino]ethyl}pyridine (4f): H NMR (400 MHz, CDCl3; δ, ppm) 2a, or 0.0182 mol (2.24 g) of p-methoxyaniline 2h, 45 mg of
8.34 (d, 2H, pym–H), 7.86 (t, 1H, pyp–H), 7.19 (d, 4H, Phm–H), p-toluenesulfonic acid monohydrate (TsOH), and 700 mg
6.78 (d, 4H, Pho–H), 2.62 (t, 4H, Ph–CH2-(CH2)3CH3), 2.42 (s, MgSO4 with (2) 11.2 mm WC balls. The reaction vessel was
6H, NvC(CH3)), 1.64 (m, 4H, Ph–CH2-(CH2)3CH3), 1.35 (brm, sealed and placed on a SPEX® 8000 mill and allowed to react
8H, Ph–CH2-(CH2)3CH3), 0.91 (brt, 12H, Ph–CH2-(CH2)3CH3). for 4 h. When complete, an aliquot of the powder/slurry was
Due to fluxionality in solution/multiple orientations of the imino- taken, dissolved in ∼0.8 mL CDCl3, and passed through a
aryl/alkyl groups, a higher number of peaks in the 13C are 0.2 μm PTFE syringe filter. The sample was measured by 1H
observed than would be expected for a symmetrical ligand: 13C NMR spectroscopy, and the % composition was determined by
{1H} NMR (100 MHz, CDCl3; δ, ppm) 166.6 (CvN), 156.2 the integration of the well-resolved pyridine meta-CH peaks
(CAryl), 152.7 (CAryl), 152.4 (CAryl), 148.6 (CAryl), 144.0 (CAryl), (Fig. S1 and S13†). 2a and 2h were isolated by the same proto-
138.5 (CAryl), 138.0 (CAryl), 133.2 (CAryl), 129.2 (CAryl), 129.0 col as described for the smaller scale reactions (vide supra).
(CAryl), 128.9 (CAryl), 124.8 (CAryl), 124.7 (CAryl), 122.5 (CAryl),
Synthesis of 2-{1-[(2,4,6-trimethylphenyl)imino]ethyl},6-{1-
119.3 (CAryl), 115.2 (CAryl), 35.4 (CAlkyl), 35.1 (CAlkyl), 31.6 [(2,6-dimethylphenyl)imino]ethyl}pyridine (4ab). In a steel
This journal is © The Royal Society of Chemistry 2018
Dalton Trans., 2018, 47, 16876–16884 | 16881