RESEARCH ARTICLE
The mixture was stirred for 24 h at 25°C. Then, the mixture
iodide (441 mg, 1.7 mmol). 0.49 g, yield: 99%. White solid, mp
1
was filtrated and washed with Et O (2 x 5 mL) and dried under
vacuum overnight to give the desired product.
168–171°C; H NMR (500 MHz, Acetone-d6) δ 9.21 (s, 4H),
2
4.86–4.74 (m, 4H), 2.28 (d, J=0.7 Hz, 12H), 2.22–2.14 (m,
4
1
H), 1.54–1.45 (m, 4H), 1.45–1.36 (m, 4H), 1.36–1.22 (m,
2H), 0.87 (t, J=6.9 Hz, 6H); C{1H} NMR (126 MHz,
3
,3’-Dibromo-5,5’-diiodo-1-methyl-[4,4’-bipyridin]-1-ium tri-
fluoromethanesulfonate (12b). Starting from bipyridine 11
100 mg, 0.18 mmol) and methyltriflate (28 mg, 0.18 mmol).
13
Acetone-d6) δ 151.7, 144.8, 137.5, 66.1, 62.8, 32.5, 32.0, 26.8,
(
19
2
3.3, 17.0, 15.6, 14.3; F NMR (471 MHz, Acetone-d6) δ
1
7
2 mg, yield: 55%. White solid, mp 183–185°C; H NMR
À 78.89; HRMS (ESI-TOF) m/z calcd for C H N : 219.1981
3
0
50
2
(300 MHz, Acetone-d6) δ 9.88–9.82 (m, 1H), 9.80–9.77 (m,
2+
À
[
M] ; found, 219.1978; m/z calcd for CF O S: 148.9526 [M] ;
1
3
3 3
1H), 9.22 (s, 1H), 9.04 (s, 1H), 4.75 (s, 3H); C{1H} NMR
found, 148.9510.
(
1
126 MHz, Acetone-d6) δ 161.3, 157.5, 154.0, 152.4, 151.9,
49.4, 122.3, 119.4, 98.7, 95.6, 49.6; F NMR (282 MHz,
1
9
3,3’-Dibromo-5,5’-diiodo-1,1’-dioctyl-[4,4’-bipyridine]-1,1’-
diium bis(trifluoromethanesulfonate) (17). Starting from
bipyridine 11 (54 mg, 0.10 mmol) n-octyltriflate (100 mg,
0.38 mmol). 60 mg, yield: 58%. White solid, mp 197–200°C;
Acetone-d6) δ À 78.82; HRMS (ESI-TOF) m/z calcd for
+
C H Br I N : 578.7060 [M] ; found, 578.7038; m/z calcd for
1
1
7
2
2
2
À
CF O S: 148.9526 [M] ; found, 148.9510.
3
3
1
H NMR (500 MHz, Acetone-d6) δ 9.99 (s, 2H), 9.93 (s, 2H),
3
,3’-Dibromo-5,5’-diiodo-1-octyl-[4,4’-bipyridin]-1-ium tri-
fluoromethanesulfonate (12c). Starting from bipyridine 11
100 mg, 0.18 mmol) and n-octyltriflate (47 mg, 0.18 mmol).
5
1
{
1
2
.03–4.93 (m, 4H), 2.35–2.23 (m, 4H), 1.55–1.49 (m, 4H),
13
.45–1.37 (m, 4H), 1.37–1.23 (m, 12H), 0.90–0.82 (m, 6H);
C
(
1H} NMR (126 MHz, Acetone-d6) δ 159.8, 153.5, 148.7,
22.2 (q, J=321.5 Hz), 122.1, 63.9, 32.4, 32.0, 29.7, 29.7,
1
1
37 mg, yield: 92%. White solid, mp 156–160°C; H NMR
(300 MHz, Acetone-d6) δ 9.93 (d, J=1.3 Hz, 1H), 9.87 (d, J=
19
6.8, 23.3, 14.3; F NMR (282 MHz, Acetone-d6) δ À 78.84;
1
2
{
1
2
.3 Hz, 1H), 9.20 (s, 1H), 9.02 (s, 1H), 5.02–4.93 (m, 2H),
+
HRMS (ESI-TOF) [M] m/z calcd for C H Br I N : 578.7060
1
3
26 38
2
2
2
.36–2.20 (m, 2H), 1.52–1.25 (m, 10H), 0.95–0.79 (m, 3H);
C
+
[M] ; found, 578.7032.
1H} NMR (126 MHz, Acetone-d6) δ 160.9, 156.7, 152.2,
[40]
51.6, 151.0, 147.6, 122.1, 118.4, 98.5, 94.9, 62.8, 31.6, 31.0,
General procedure for the synthesis of imines 19.
A
1
9
8.9, 28.8, 25.9, 22.4, 13.5; F NMR (282 MHz, Acetone-d6) δ
mixture of MgSO (1 g) in DCM (10 mL) was stirred for 10
4
À 78.79; HRMS (ESI-TOF) m/z calcd for C H Br I N :
minutes at room temperature. The relevant aldehyde (10 mmol,
1 eq.) and amine (10 mmol, 1 eq.) were sequentially added. The
reaction was stirred under argon for 18 h. The mixture was
diluted with DCM and then filtered. The filtrate was concen-
trated to give crude imine which was used without further
1
8
21
2
2
2
+
6
1
76.8155 [M] ; found, 676.8155; m/z calcd for CF O S:
3 3
À
48.9526 [M] ; found, 148.9527.
General procedure for the synthesis of 15a,b, 16and 17.
Bipyridine 11, 13 or 14 (1 eq.) was solubilized in CH CN
1
3
purification. Purity >95% was evidenced by H NMR for all
imines.
(
2 mL) and placed in a tube equipped with a magnetic stir bar.
The electrophile (n-octyl iodide or n-octyl triflate) was added
3 eq.) and the tube was sealed with a screw cap. The mixture
(
General procedure for the aza Diels-Alder reaction. In a
round-bottom flask under argon at 25°C, the imine (0.5 mmol)
was stirred for 24 h at 120°C. After cooling to room temper-
ature, the mixture was filtrated and washed with Et O (2 x
was diluted in dry CH Cl (2.5 mL) and trans-1-methoxy-3-
2
2
2
5
mL) and dried under vacuum overnight to give the desired
trimethylsiloxy-1,3-butadiene 18 was added. The catalyst
(0.025 mmol) diluted in dry dichloromethane (0.5 mL) was
added and the mixture was stirred for 1 h. The reaction was
quenched by addition of 1 mL of TBAF (1.0 M in THF) and the
mixture was stirred for 15 min. Water (10 mL) was added and
the phases were separated. The aqueous phase was extracted
product.
[39]
1,1’-Dioctyl-[4,4’-bipyridine]-1,1’-diium bis(iodide) (15a).
Starting from 4,4’-bipyridine (0.2 g, 1.3 mmol) and n-octyl
1
iodide (0.63 g, 2.6 mmol). 0.82 g, yield: 99%. White solid. H
NMR (500 MHz, CD OD) δ 9.30 (d, J=6.9 Hz, 3H), 8.70 (d,
3
with CH Cl2 (3×15 mL) then the organic phases were
2
J=6.3 Hz, 4H), 4.76 (t, J=7.6 Hz, 4H), 2.10 (q, J=7.6 Hz,
combined and dried over MgSO . After filtration and concen-
1
3
4
4
H), 1.54–1.21 (m, 20H), 0.91 (t, J=6.7 Hz, 6H); C{1H}
tration, the crude was purified by chromatography on silica gel
NMR (126 MHz, CD OD) δ 151.3, 147.1, 128.4, 63.3, 32.9,
3
(cyclohexane / ethyl acetate mixture) to give pure product.
32.6, 30.2, 30.1, 27.3, 23.7, 14.4.
[
41]
1
,2-Diphenyl-2,3-dihydropyridin-4(1H)-one (20a). Yellow
1,1’-Dioctyl-[4,4’-bipyridine]-1,1’-diium bis(trifluoro-metha-
1
solid; 118 mg (95%) with 15b and 116 mg (93%) with 12c. H
nesulfonate) (15b). Starting from 4,4’-bipyridine (0.2 g,
NMR (500 MHz, CDCl ) δ 7.68 (dd, J=8.0, 1.4 Hz, 1H), 7.38–
3
1
.3 mmol) and n-octyl triflate (0.63 g, 2.6 mmol). 0.87 g, yield:
7
.20 (m, 5H), 7.11 (t, J=7.3 Hz, 1H), 7.02 (d, J=8.7, 2H),
1
98%. H NMR (500 MHz, DMSO-d6) δ 9.36 (d, J=6.5 Hz,
5
.33–5.24 (m, 2H), 3.31 (dd, J=16.4, 7.2 Hz, 1H), 2.79 (ddd,
4
H), 8.76 (d, J=6.4 Hz, 4H), 4.67 (t, J=7.4 Hz, 4H), 1.97 (t,
13
J=16.4, 3.1, 1.2 Hz, 1H); C{1H} NMR (126 MHz, CDCl ) δ
1
3
3
J=7.1 Hz, 4H), 1.40–1.20 (m, 20H), 0.95–0.76 (m, 6H);
C
1
90.4, 148.3, 144.8, 138.0, 129.7, 129.1, 128.0, 126.3, 124.5,
{
1H} NMR (126 MHz, DMSO-d6) δ 148.7, 145.8, 126.7, 120.7
118.6, 103.2, 61.8, 43.6.
(
q, J=322.3 Hz), 61.0, 31.2, 30.8, 28.5, 28.4, 25.5, 22.1, 14.0;
19
[41]
F NMR (471 MHz, DMSO-d6) δ À 77.8. HRMS (ESI-TOF)
1-Phenyl-2-(p–tolyl)-2,3-dihydropyridin-4(1H)-one (20b).
2
+
m/z calcd for C H N : 191.1669 [M] ; found, 191.1666; m/z
calcd for CF O S: 148.9526 [M] ; found, 148.9526.
Yellow solid; 122 mg (93%) with 15b and 118 mg (90%) with
26
42
2
À
1
12c. H NMR (500 MHz, CDCl ) δ 7.67 (dd, J=7.8, 1.2 Hz,
3
3
3
1
H), 7.30 (dd, J=8.7, 7.5 Hz, 2H), 7.17–7.08 (m, 5H), 7.03
3
,3’,5,5’-Tetramethyl-1,1’-dioctyl-[4,4’-bipyridin]-1-diium bis
(dd, J=8.7, 1.2 Hz, 2H), 5.31–5.23 (m, 2H), 3.28 (dd, J=16.3,
(trifluoromethanesulfonate) (16). Starting from 3,3’,5,5’-
7
.0 Hz, 1H), 2.77 (ddd, J=16.3, 3.4, 1.2 Hz, 1H), 2.31 (s, 3H);
tetramethyl-4,4’-bipyridine (143 mg, 0.67 mmol) and n-octyl
Adv. Synth. Catal. 2021, 363, 1–11
8
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