Double Heck cross-coupling reactions of dibrominated pyridines

Article abstract of DOI:10.1002/hlca.201000108

Double Heck cross-coupling reactions of 2,3- and 3,5-dibromopyridine with various alkenes afforded the corresponding novel di(alkenyl)pyridines. The Heck reaction of 2,5-dibromopyridine unexpectedly afforded 5,5′-di(alkenyl)-2, 2′-bipyridines by palladium

Full text of DOI:10.1002/hlca.201000108

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Helvetica Chimica Acta – Vol. 93 (2010)
Double Heck Cross-Coupling Reactions of Dibrominated Pyridines
by Asad Alia), Munawar Hussaina), Imran Malika), Alexander Villingera), Christine Fischerb), and
Peter Langer*a)b)
a) Institut fꢀr Chemie, Universitꢁt Rostock, Albert-Einstein-Strasse 3a, D-18059 Rostock
(fax: þ 49-381-498-6412; e-mail: peter.langer@uni-rostock.de)
b) Leibniz Institut fꢀr Katalyse and der Universitꢁt Rostock e.V., Albert-Einstein-Strasse 29a,
D-18059 Rostock
Double Heck cross-coupling reactions of 2,3- and 3,5-dibromopyridine with various alkenes
afforded the corresponding novel di(alkenyl)pyridines. The Heck reaction of 2,5-dibromopyridine
unexpectedly afforded 5,5’-di(alkenyl)-2,2’-bipyridines by palladium-catalyzed dimerization to give 5,5’-
dibromo-2,2’-bipyridine and subsequent twofold Heck reaction.
Introduction. – In recent years, site-selective reactions of polyhalogenated hetero-
cycles have been intensively studied [1][2]. Cross-coupling reactions of 2,5-dibromo-
pyridine include aminations [3], and Stille [4], Suzuki [5], Negishi [6], Sonogashira [7],
and Kumada couplings [8]. In all cases, the first reaction occured at the more electron-
deficient position C(2). In most studies, single coupling reactions were carried out.
Recently, Handy et al. reported the first double Suzuki couplings of 2,5- and 2,3-
dibromopyridine, and of several other heterocycles [9a]. Cid and co-workers also
reported interesting work in this field [9b,c]. Single Heck coupling reactions of 2-
chloro- and 2-bromopyridine have been studied in recent years [10]. Here, we report
double Heck reactions of 2,3-, 2,4-, and 3,5-dibromopyridine [10f].
Results and Discussion. – The Heck reaction of 2,3-dibromopyridine (1a) with
acrylates 2a – 2e afforded the 2,3-di(alkenyl)pyridines 3a – 3e (Table 1). The reaction of
1a with styrenes 2f – 2i gave products 3f and 3h – 3i (3g could not be isolated due to
decomposition during the reaction). All products were isolated in 60 – 84% yield and
contain exclusively (E)-configured C¼C bonds. The reaction of 2f and 2i with 2,3-
dichloropyridine (1b) instead of 1a afforded 3f and 3i, respectively, albeit, in only poor
yields. The reaction conditions were thoroughly optimized for the synthesis of 3c and 3f
(Fig. 1, Table 2). The best yields were obtained when the reactions were carried out
with 1a, Pd(OAc)2 (5 mol-%), and the biaryl-monophosphine ligands SPhos (L1, for
3a – 3g and 3i) or XPhos (L2, for 3h) (10 mol-%) which were both recently developed
by Billingsley and Buchwald (Fig. 1) [11]. The use of tris(cyclohexyl)phosphane (L4)
gave slightly lower yields. Employing Pd(Ph3P)4 resulted in considerably lower yields.
Et3N was used as the base in all reactions. The application of other bases (K2CO3) did
not lead to an increase of the yield. The reactions were carried out in DMF at 1208. A
relatively long reaction time (48 h) was necessary to achieve a complete conversion.
Recently, Li and Wang reported [12] that triethanolamine (L3) represents an efficient
ꢂ 2010 Verlag Helvetica Chimica Acta AG, Zꢀrich

Helvetica Chimica Acta – Vol. 93 (2010)
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Table 1. Synthesis of 2,3-Di(alkenyl)pyridines 3a – 3i
X of 1
R of 2 and 3
2, 3
Yield of 3 [%]a)
Br
Br
Br
Br
Br
Br
Cl
Br
Br
Br
Cl
CO2Me
a
b
c
d
e
f
63
71
82
84
60
72
11
0c)
79d)
65
9
CO2Et
CO2iBu
CO2tBu
CO2Rb)
Ph
Ph
f
4-tBuOꢀC6H4
4-MeOꢀC6H4
4-MeꢀC6H4
4-MeꢀC6H4
g
h
i
i
a) Yields of isolated products. b) R ¼ Me(CH2)3CH(Et)CH2. c) Decomposition. d) Ligand L2 was used.
Fig. 1. Ligands Used in This Study
Table 2. Optimization of the Syntheses of 2,3-Di(alkenyl)pyridines 3c and 3f
Conditions
3c [%]a)
3f [%]a)
Pd(Ph3P)4 (5 mol-%), Et3N, DMF, 1208, 48 h
38
72
82
80
2
49
63
72
69
10
Pd(OAc)2 (5 mol-%), Cy3P (10 mol-%), Et3N, DMF, 1208, 48 h
Pd(OAc)2 (5 mol-%), L1 (10 mol-%), Et3N, DMF, 1208, 48 h
Pd(OAc)2 (5 mol-%), L2 (10 mol-%), Et3N, DMF, 1208, 48 h
Pd(OAc)2 (5 mol-%), (HOCH2CH2)3N (3 ml), 1208, 48 h
a) Yields of isolated products.

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Helvetica Chimica Acta – Vol. 93 (2010)
and reusable combined base, ligand, and solvent for Heck reactions. However, only
traces of the product could be isolated when these conditions were applied. The
synthesis of 2,3-di(alkenyl)pyridines has, to the best of our knowledge, not been
previously reported.
The double Heck reaction of 3,5-dibromopyridine (4) with acrylates 2a – 2d, 2f, and
2i – 2k, using Pd(OAc)2 and L4, afforded the 3,5-di(alkenyl)pyridines 5a – 5h in 69 –
84% yield (Table 3). Similar yields were obtained by using ligands L4 and L1.
Therefore, the cheaper ligand L4 was employed. The synthesis of 5c and 5g by Heck
reactions has been previously reported by Santelli and co-workers [10f]. The structure
of 5g was independently confirmed by X-ray crystal structure analysis (Fig. 2)1).
Table 3. Synthesis of 3,5-Di(alkenyl)pyridines 5a – 5h
2
5
R
Yield of 5 [%]a)
a
b
j
c
k
d
f
a
b
c
d
e
f
CO2Me
CO2Et
CO2Bu
69
71
82
84
77
81
72
76
i
CO2 Bu
CO2Hex
t
CO2 Bu
g
h
Ph
i
4-MeꢀC6H4
a) Yields of isolated products.
The Heck reaction of 2,5-dibromopyridine (6) with acrylates 2c – 2e and 2i – 2k
unexpectedly afforded the 5,5’-di(alkenyl)-2,2’-bipyridines 7a – 7f in 60 – 84% yield
(Table 4). The best yields were obtained with Pd(OAc)2 and L2. The synthesis of 2,5-
di(alkenyl)pyridines by double Heck reaction was not possible under various
conditions (different catalysts and temperatures). The formation of 7a – 7f can be
explained by Pd-catalyzed dimerization to give 5,5’-dibromo-2,2’-bipyridine and
subsequent twofold Heck reaction. The Pd-catalyzed dimerization seems to be faster
than the Heck reaction. The formation of 2,2’-bipyridines as side-products in Heck
reactions of 2-bromopyridine [10] and in Suzuki – Miyaura reactions of 2,4-dibromo-
pyridine have been previously reported. The structure of 7d was independently
confirmed by X-ray crystal structure analysis (Fig. 3).
1
)
CCDC-779693 and -779694 contain crystallographic data for 7d and 5g, respectively. These data can
be obtained free of charge via http://www.ccdc.cam.ac.uk/data_request/cif (or from the Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge CB21EZ, UK; fax: þ44-1223-336033;
e-mail: deposit@ccdc.cam.ac.uk).

Helvetica Chimica Acta – Vol. 93 (2010)
1767
Fig. 2. ORTEP Plot of 5g
Table 4. Synthesis of Bipyridines 7a – 7f
2
7
R
Yield of 7 [%]a)
j
a
b
c
d
e
f
CO2Bu
83
71
82
84
77
60
k
e
d
c
i
CO2Hex
CO2Rb)
t
CO2 Bu
i
CO2 Bu
4-MeꢀC6H4
a) Yield of isolated products. b) R ¼ Me(CH2)3CH(Et)CH2.
In conclusion, we have reported the first double Heck cross-coupling reactions of
2,3- and 3,5-dibromopyridine with various alkenes. These reactions afforded the
corresponding di(alkenyl)pyridines. The Heck reaction of 2,5-dibromopyridine gave
5,5’-di(alkenyl)-2,2’-bipyridines by Pd-catalyzed dimerization and subsequent twofold
Heck reaction of 5,5’-dibromo-2,2’-bipyridine thus formed.
Experimental Part
General. All cyclization reactions were carried out in pressure tubes under Ar. M.p.: Microheating
table HMK 67/1825 Kuestner (Bꢀchi apparatus); uncorrected. Anal. TLC: 60A silica-gel plates (SiO2;
0.20 mm). Flash column chromatography (FC): 60A SiO2 (60 – 200 mesh). IR Spectra: Nicolet 380 FT-IR
1
spectrometer, KBr pellets; ˜n in cmꢀ1. H- and 13C-NMR spectra: Bruker AVANCE 300 II and Bruker
AVANCE 250 II spectrometer in CDCl3; d in ppm rel. to solvent as internal standard (d(H) 7.26 and
d(C) 77.0 ppm), J in Hz. EI-MS and HR-EI-MS: Finnigan MAT 95-XP mass spectrometer at 70 eV;
in m/z.

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Fig. 3. ORTEP Plot of 7d
General Procedure for Double Heck Cross-Coupling Reactions. In a pressure tube (glass bomb), a
suspension of Pd(OAc)2 (12 mg, 0.05 mmol, 2.5 mol-% per Br) and dicyclohexyl(2’,4’,6’-triisopropyl-1,1’-
biphenyl-2-yl)phosphane (L2; 47 mg, 0.10 mmol) or the same amount of another indicated ligand in
DMF (5 ml) was purged with Ar and stirred at 208 to give a yellowish or brownish transparent soln. To
the stirred soln. were added the 2,3- or 3,5- or 2,5-dibromopyridine (1a or 4 or 6, resp. 237 mg, 1,0 mmol),
Et3N (1.1 ml, 8.0 mmol), and the acrylate or styrene (1.25 equiv. per Br). The mixture was stirred at 1208
for 48 h. The soln. was cooled to 208, poured into H2O and CH2Cl2 (25 ml each), and the org. and the aq.
layer were separated. The latter was extracted with CH2Cl2 (3 ꢁ 25 ml). The combined org. layers were
washed with H2O (3 ꢁ 20 ml), dried (Na2SO4), filtered, and concentrated in vacuo. The residue was
purified by FC on SiO2 (heptanes/AcOEt): compounds 3, 5, or 7.
Dimethyl 3,3’-Pyridine-2,3-diylbis[(E)-prop-2-enoate] (3a). Light yellow oil (175 mg, 71%). IR:
2955w, 2929w, 2852w, 1722s, 1709s, 1634m, 1580w, 1555w, 1434s, 1361w, 1300w, 1275w, 1194w, 1161s, 1086s,
1
1064s, 1010s, 990w, 970m, 932m, 870m, 778m, 732m, 720m, 702m, 605m, 582m, 568m, 544w. H-NMR
(300 MHz): 3.76 (s, MeO); 3.77 (s, MeO); 6.34 (d, J ¼ 15.2, CH); 7.01 (d, J ¼ 15.6, CH); 7.22 – 7.26 (m, 1
arom. H); 7.77 (dd, J ¼ 1.5, 8.2, 1 arom. H); 7.93 (d, J ¼ 15.4, CH); 8.00 (d, J ¼ 15.4, CH); 8.56 (dd, J ¼ 1.7,
4.6, 1 arom. H). 13C-NMR (62.9 MHz): 51.8, 51.9 (MeO); 123.0, 124.3, 124.6 (CH); 130.1 (C); 134.9,
138.6, 139.2, 150.7 (CH); 150.9, 166.2, 167.0 (C). GC/EI-MS: 247 (2, Mþ), 216 (19), 188 (100), 156 (28),
144 (24), 78 (6). HR-EI-MS: 247.08462 (Mþ, C13H13NO4þ ; calc. 247.08446).
Diethyl 3,3’-Pyridine-2,3-diylbis[(E)-prop-2-enoate] (3b). White solid (195 mg, 71%). M.p. 145 –
1478. IR: 1705s, 1631s, 1580w, 1552w, 1473w, 1446w, 1423m, 1364m, 1295s, 1228m, 1661s, 1112w, 1065w,
1027s, 971s, 892s, 872s, 808s, 782s, 722m, 709m, 602m, 580m, 546m. 1H-NMR (300 MHz): 1.26 (t, J ¼ 7.1,
Me); 1.27 (t, J ¼ 7.1, Me); 4.19 (q, J ¼ 7.1, 14.3, CH2O); 4.22 (q, J ¼ 7.1, 14.3, CH2O); 6.30 (d, J ¼ 15.2,
CH); 6.99 (d, J ¼ 15.2, CH); 7.20 – 7.25 (m, 1 arom. H); 7.76 (dd, J ¼ 1.4, 8.1, 1 arom. H); 7.89 – 7.99 (m, 2
arom. H); 8.53 (dd, J ¼ 1.6, 4.6, 1 arom. H). 13C-NMR (75 MHz): 14.2 (2 Me); 60.7, 60.8 (CH2O); 123.5,
124.3, 125.1 (CH); 130.1 (C); 134.9, 138.4, 150.7 (CH); 150.8 (C); 165.8, 166.5 (C¼O). GC/EI-MS: 275
(3, Mþ), 246 (2), 230 (30), 202 (100), 174 (48), 156 (33), 130 (71), 77 (9). HR-EI-MS: 275.11549 (Mþ,
C15H17NOþ4 ; calc. 275.11576).
Bis(2-methylpropyl) 3,3’-Pyridine-2,3-diylbis[(E)-prop-2-enoate] (3c). Light-yellow semisolid
(271 mg, 82%). IR: 2960m, 2874m, 1712s, 1635m, 1469m, 1424m, 1376m, 1369m, 1305s, 1292s, 1276s,
1256s, 1158s, 1010s, 973s, 802m, 780m, 702m, 606m, 590m. 1H-NMR (300 MHz): 0.89 (d, J ¼ 6.8, 2 Me);
0.93 (d, J ¼ 6.7, 2 Me); 1.90 – 2.00 (m, 2 H); 3.93 (d, J ¼ 6.7, CH2); 3.96 (d, J ¼ 6.7, CH2); 6.33 (d, J ¼ 15.6,

Helvetica Chimica Acta – Vol. 93 (2010)
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1 H); 7.01 (d, J ¼ 15.9, 1 H); 7.20 – 7.25 (m, 1 arom. H); 7.80 (dd, J ¼ 1.5, 8.0, arom. H); 7.95 (d, J ¼ 15.2,
H); 8.00 (d, J ¼ 15.8, H); 8.55 (dd, J ¼ 1.6, 4.5, arom. H). 13C-NMR (75 MHz): 19.0, 19.1 (Me); 27.8 (CH);
70.8, 71.0 (CH2O); 123.5, 124.3, 125.2 (CH); 130.1 (C); 135.0, 138.4, 139.0, 150.6 (CH); 150.8, 165.1, 165.8
(C). GC/EI-MS: 331 (2, Mþ), 258 (46), 230 (100), 202 (29), 174 (81), 156 (19), 129 (38). HR-EI-MS:
331.17745 (Mþ, C19H25NOþ4 ; calc. 331.17836).
Di(tert-butyl) 3,3’-Pyridine-2,3-diylbis[(E)-prop-2-enoate] (3d). Light-yellow solid (278 mg, 84%).
M.p. 137 – 1388. IR: 3004w, 2978w, 2930w, 2871w, 1698s, 1634w, 1578w, 1552w, 1471w, 1456w, 1422m,
1392m, 1365m, 1392m, 1365s, 1309s, 1254s, 1138s, 1086w, 1062w, 1039w, 971s, 922m, 889m, 845m, 805m,
763m, 731m, 598m, 538m. 1H-NMR (300 MHz): 1.43 (s, 3 Me); 1.44 (s, 3 Me); 6.22 (d, J ¼ 15.2, CH); 6.90
(d, J ¼ 15.9, CH); 7.17 – 7.22 (m, 1 arom. H); 7.73 (dd, J ¼ 1.7, 8.0, 1 arom. H); 7.84 (d, J ¼ 15.2, CH); 7.86
(d, J ¼ 15.8, CH); 8.50 (dd, J ¼ 1.7, 4.6, 1 arom. H). 13C-NMR (62.9 MHz): 28.0 (3 Me); 28.1 (3 Me); 80.7,
81.0 (C); 124.0, 125.3, 127.0 (CH); 130.1 (C); 134.9, 137.6, 138.0, 150.4 (CH); 150.9 (CH); 164.9, 165.7
(C¼O). GC/EI-MS: 331 (1, Mþ), 275 (1), 230 (23), 202 (39), 174 (99), 130 (100), 102 (10), 57 (91). HR-
EI-MS: 331.17840 (Mþ, C19H25NO4þ ; calc. 331.17836).
Bis(2-ethylhexyl) 3,3’-Pyridine-2,3-diylbis[(E)-prop-2-enoate] (3e). Light-yellow oil (265 mg, 60%).
IR: 2957m, 2927m, 2872m, 2869m, 1713s, 1636w, 1580w, 1554w, 1460w, 1425w, 1380w, 1296m, 1260m,
1220w, 1204 w, 1163s, 1085w, 1063w, 1027w, 1014w, 974m, 918w, 869w, 801w, 780m, 729w, 703w, 606w.
1H-NMR (300 MHz): 0.82 – 0.87 (m, 4 Me); 1.27 – 1.31 (m, 6 CH2); 1.28 – 1.31 (m, 2 CH2); 1.33 – 1.60 (m,
2 CH); 4.06 – 4.09 (m, 2 CH2O); 6.31 (d, J ¼ 15.2, CH); 7.01 (d, J ¼ 15.2, CH); 7.20 – 7.25 (m, 1 arom. H);
7.78 (dd, J ¼ 1.5, 8.0, 1 arom. H); 7.92 (d, J ¼ 15.2, CH); 7.97 (d, J ¼ 15.2, CH); 8.55 (dd, J ¼ 1.8, 4.5, 1
arom. H). 13C-NMR (62.9 MHz): 10.9, 11.0, 14.0 (Me); 22.9, 23.8 28.9, 30.4 (CH2); 38.7, 38.8 (CH); 67.1,
67.4 (CH2O); 123.6, 124.2, 125.2 (CH); 138.3 (C); 135.0, 138.4, 138.9, 150.6 (CH); 150.9 (C); 165.9, 166.6
(C¼O). GC/EI-MS: 443 (2, Mþ), 398 (4), 332 (42), 286 (100), 202 (48), 70 (16), 57 (29). HR-EI-MS:
443.30301 (Mþ, C27H41NOþ4 ; calc. 443.30356).
2,3-Bis[(E)-2-phenylethenyl]pyridine (3f). Light-yellow solid (204 mg, 72%). M.p. 130 – 1328. IR:
3078w, 3055w, 3024w, 2929w, 1732w, 1699w, 1628w, 1597w, 5174w, 1492m, 1448m, 1419m, 1371w, 1323w,
1300w, 1271w, 1240w, 1203w, 1179w, 1162w, 1072w, 1045w, 1027w, 958s, 915w, 847w, 770s, 744s, 687s, 543m.
1H-NMR (300 MHz): 6.88 (d, J ¼ 15.2, CH); 7.06 (dd, J ¼ 7.9, 4.5, 1 arom. H); 7.21 – 7.31 (m, 6 arom. H);
7.36 – 7.45 (m, 4 arom. H); 7.49 – 7.52 (m, 2 arom. H); 7.69 – 7.74 (m, 2 arom. H); 8.44 (dd, J ¼ 1.8, 4.5, 1
arom. H). 13C-NMR (62.9 MHz): 122.3, 124.2, 124.4, 126.8, 127.3, 128.3, 128.4, 128.7, 128.9 (CH); 131.4
(C); 133.1, 134.4, 134.7 (CH); 137.0, 148.4, 152.5 (C). GC/EI-MS: 283 (100, Mþ), 206 (42), 180 (7), 134
(6), 91 (4), 77 (3). HR-EI-MS: 282.12783 ([M ꢀ 1]þ, C21H16Nþ; calc. 282.12827).
2,3-Bis[(E)-2-(4-methoxyphenyl)ethenyl]pyridine (3h). Light-yellow crystalline solid (271 mg,
79%). M.p. 123 – 1248. IR: 3045w, 3000w, 2668w, 2932w, 2836w, 1692w, 1626w, 1600m, 1572m, 1550w,
1508s, 1464m, 1455m, 1439m, 1426m, 1344w, 1332w, 1245s, 1170s, 1023m, 967m, 936w, 856w, 818s, 791m,
775m, 715w, 688w, 612w. 1H-NMR (300 MHz): 3.75 (s, MeO); 3.76 (s, MeO); 6.81 – 6.88 (m, 5 arom. H);
7.03 – 7.07 (m, 1 arom. H); 7.30 (d, J ¼ 15.7, CH); 7.31 (d, J ¼ 15.2, CH); 7.39 – 7.49 (m, 4 arom. H); 7.64 (d,
J ¼ 15.2, CH); 7.72 (dd, J ¼ 1.6, 8.0, 1 arom. H); 8.42 (dd, J ¼ 1.5, 4.6, 1 arom. H). 13C-NMR (62.9 MHz):
55.3, 55.3 (MeO); 114.1, 114.2, 121.9, 122.1, 122.3, 127.9, 128.6 (CH); 129.3, 130.3 (C); 132.3, 133.9, 134.1,
148.0 (CH); 156.0, 159.7, 159.9 (C). GC/EI-MS: 343 (100, Mþ), 236 (72), 222 (9), 121 (31), 77 (2). HR-
EI-MS: 343.15642 (Mþ, C23H21NO2þ ; calc. 343.15723).
2,3-Bis[(E)-2-(4-methylphenyl)ethenyl]pyridine (3i). Light-yellow semi-solid (202 mg, 65%). IR:
3031w, 2919w, 2853w, 2727w, 1693w, 1626w, 1605w, 1573w, 1550w, 1450w, 1422m, 1324w, 1298w, 1200w,
1182w, 1109w, 1082w, 1039w, 1018w, 959s, 867w, 805s, 706w, 635w, 613w, 548w, 533m. 1H-NMR
(300 MHz): 2.27 (s, Me); 2.28 (s, Me); 6.85 (d, J ¼ 15.2, CH); 7.03 – 7.14 (m, 5 arom. H); 7.32 – 7.43 (m, 6
arom. H); 7.64 – 7.72 (m, 2 arom. H); 8.42 (dd, J ¼ 1.5, 4.5, 1 arom. H). 13C-NMR (75 MHz): 21.3, 21.4
(Me); 122.0, 123.3, 123.5, 126.6, 127.2, 129.4 (CH); 129.5 (C); 129.6 (CH); 131.5 (C); 132.8, 134.2 (CH);
134.3 (C); 134.5 (CH); 138.2, 138.4 (C); 148.2 (CH); 152.6 (C). GC/EI-MS: 311 (60, Mþ), 310 (100), 220
(45), 147 (6), 105 (9). HR-EI-MS: 311.15912 (Mþ, C23H21Nþ; calc. 311.16740).
Dimethyl 3,3’-Pyridine-3,5-diylbis[(E)-prop-2-enoate] (5a). White solid (170 mg, 69%). M.p. 156 –
1588. IR: 2954m, 2921m, 2851m, 1722s, 1716s, 1642s, 1433m, 1329m, 1316m, 1329m, 1315m, 1292w, 1278w,
1244m, 1189m, 1169s, 1025w, 1014w, 999w, 977m, 854m, 785w, 738w, 727w, 704w, 688m, 600m. 1H-NMR
(300 MHz): 3.76 (s, 2 MeO); 6.46 (d, J ¼ 16.1, 2 CH); 7.62 (d, J ¼ 16.1, 2 CH); 7.86 (br. s, 1 arom. H); 8.66

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(s, 2 arom. H). 13C-NMR (62.9 MHz): 60.0 (MeO); 121.1, 132.2 (CH); 132.6 (C); 140.3, 150.3 (CH); 166.4
(C¼O). GC/EI-MS: 247 (70, Mþ), 232 (64), 216 (100), 200 (30), 184 (72), 156 (46), 128 (31). HR-EI-
MS: 247.08498 (Mþ, C13H13NOþ4 ; calc. 247.08446).
Diethyl 3,3’-Pyridine-3,5-diylbis[(E)-prop-2-enoate] (5b). White solid (195 mg, 71%). M.p. 162 –
1638. IR: 2982w, 2934w, 2904w, 2874w, 1699s, 1639m, 1592w, 1567w, 1420m, 1368m, 1321m, 1239m,
1167s, 1094m, 977s, 911w, 854s, 810w, 686m, 605w, 587w, 541w. 1H-NMR (300 MHz): 1.27 (t, J ¼ 7.0,
2 Me); 4.22 (q, J ¼ 7.1, 14.3, 2 CH2O); 6.48 (d, J ¼ 16.1, 2 CH); 7.60 (d, J ¼ 16.1, 2 CH); 7.88 (s, 1 arom. H);
8.66 (s, 2 arom. H). 13C-NMR (62.9 MHz): 14.2 (Me); 60.9 (CH2O); 121.5 (CH); 130.5 (C); 132.4, 140.0,
150.2 (CH); 156.9 (C¼O). GC/EI-MS: 275 (51, Mþ), 246 (61), 230 (100), 200 (44), 184 (42), 128 (14), 51
(7). HR-EI-MS: 275.11571 (Mþ, C15H17NO4þ ; calc. 275.11576).
Dibutyl 3,3’-Pyridine-3,5-diylbis[(E)-prop-2-enoate] (5c). White solid (271 mg, 82%). M.p. 148 –
1498. IR: 2957s, 2933s, 2872s, 1708s, 1638m, 1567w, 1465w, 1448w, 1432w, 1382w, 1355w, 1342w, 1312m,
1285m, 1258m, 1239m, 1168s, 1062 m, 978s, 901w, 858s, 735w, 702w, 683m, 602w, 589w. 1H-NMR
(300 MHz): 0.89 (t, J ¼ 7.4, 2 Me); 1.30 – 1.42 (m, 2 CH2); 1.57 – 1.67 (m, 2 CH2); 4.15 (t, J ¼ 6.7, 2 CH2O);
6.49 (d, J ¼ 16.1, 2 CH); 7.63 (d, J ¼ 16.1, 2 CH); 7.89 (s, 1 arom. H); 8.66 (s, 2 arom. H). 13C-NMR
(75 MHz): 13.6 (Me); 19.1, 30.7 (CH2); 64.8 (CH2O); 121.4 (CH); 130.4 (C); 132.3, 139.9, 150.3 (CH);
166.0 (C¼O). GC/EI-MS: 331 (12, Mþ), 258 (100), 230 (22), 202 (53), 184 (35), 156 (22), 128 (17). HR-
EI-MS: 331.17819 (Mþ, C19H25NO4þ ; calc. 331.17836).
Bis(2-methylpropyl) 3,3’-Pyridine-3,5-diylbis[(E)-prop-2-enoate] (5d). White solid (278 mg, 84%).
M.p. 147 – 1488. IR: 2956m, 2872m, 1708s, 100s, 1638m, 1573w, 1558w, 1470m, 1435m, 1375m, 1312m,
1293m, 1273m, 1256m, 1240m, 1170s, 1020s, 980s, 858s, 799w, 732w, 706w, 682s, 590w, 552w, 534w.
1H-NMR (300 MHz): 0.90 (d, J ¼ 6.8, 4 Me); 1.88 – 2.00 (m, 2 CH); 3.92 (d, J ¼ 6.7, 2 CH2O); 6.51 (d, J ¼
16.1, 2 CH); 7.60 (d, J ¼ 16.1, 2 CH); 7.92 (s, 1 arom. H); 8.68 (s, 2 arom. H). 13C-NMR (75 MHz): 19.0
(Me); 27.8 (CH); 70.9 (CH2O); 121.4 (CH); 130.6 (C); 132.3, 140.0, 150.3 (CH); 166.0 (C¼O). GC/EI-
MS: 331 (6, Mþ), 276 (27), 258 (100), 220 (61), 202 (30), 184 (20), 156 (13), 56 (10). HR-EI-MS:
331.40611 (Mþ, C19H25NOþ4 ; calc. 331.17836).
Dihexyl 3,3’-Pyridine-3,5-diylbis[(E)-prop-2-enoate] (5e). White solid (299 mg, 77%). M.p. 130 –
1328. IR: 2954m, 2927m, 2857m, 1712s, 1644m, 1589w, 1566w, 1464w, 1421w, 1343w, 1316m, 1258s,
1
1227m, 1166s, 1068m, 1040m, 1023m, 993s, 980s, 903m, 866m, 857m, 794m, 613w, 603w, 545w. H-NMR
(300 MHz): 0.82 (t, J ¼ 6.8, 2 Me); 1.16 – 1.35 (m, 6 CH2); 1.58 – 1.65 (m, 2 CH2); 4.14 (t, 2 CH2O); 6.49 (d,
J ¼ 16.1, 2 CH); 7.59 (d, J ¼ 16.1, 2 CH); 7.90 (br. s, 1 arom. H); 8.65 (s, 2 arom. H). 13C-NMR (75 MHz):
13.2 (Me); 21.5, 24.6, 27.6, 30.4 (CH2); 63.6 (CH2O); 120.5 (CH); 129.3 (C); 131.3, 139.0, 149.3 (CH);
165.0 (C¼O). GC/EI-MS: 387 (8, Mþ), 330 (8), 304 (50), 286 (100), 258 (30), 220 (88), 202 (51), 184
(26). HR-EI-MS: 387.240367 (Mþ, C23H33NOþ4 ; calc. 387.24096).
Di(tert-butyl) 3,3’-Pyridine-3,5-diylbis[(E)-prop-2-enoate] (5f). White solid (268 mg, 81%). M.p.
135 – 1368. IR: 2974m, 2929m, 2871m, 1698s, 1644m, 1573w, 1454w, 1433w, 1391m, 1365m, 1328m, 1295m,
1279m, 1256m, 1147s, 1040w, 1025w, 970s, 857m, 848m, 807w, 782w, 761w, 724w, 687m, 605w, 591w, 540w.
1H-NMR (300 MHz): 1.47 (s, 6 Me); 6.41 (d, J ¼ 16.1, 2 CH); 7.49 (d, J ¼ 16.1, 2 CH); 7.84 (br. s, 1 arom.
H); 8.62 (s, 2 arom. H). 13C-NMR (62.9 MHz): 28.0 (Me); 81.06 (CꢀO); 123.3 (CH); 130.5 (C); 132.1,
139.0, 150.1 (CH); 165.2 (C¼O). GC/EI-MS: 331 (20, Mþ), 275 (20), 258 (88), 220 (99), 202 (60), 173
(33), 57 (100). HR-EI-MS: 331.17831 (Mþ, C19H25NO4þ ; calc. 331.17836).
3,5-Bis[(E)-2-phenylethenyl]pyridine (5g; see also Fig. 2)1). White solid (204 mg, 72%). M.p. 115 –
1168. IR: 3098w, 3080w, 3052w, 3023w, 2926w, 2850w, 1446m, 1414w, 1340w, 1309w, 1239w, 1230w, 1178w,
1155w, 1107w, 1023w, 999w, 983w, 962s, 919w, 892w, 825w, 833w, 797w, 779w, 745s, 691s, 545m, 526m.
1H-NMR (300 MHz): 6.93 (d, J ¼ 16.4, 2 CH); 7.08 (d, J ¼ 16.4, 2 CH); 7.17 – 7.31 (m, 6 arom. H); 7.39 –
7.44 (m, 4 arom. H); 7.78 (s, 1 arom. H); 8.51 (s, 2 arom. H). 13C-NMR (75.5 MHz): 124.7, 126.8, 128.25,
128.8, 129.4, 131.1 (CH); 133.1, 136.7 (C); 147.2 (CH). GC/EI-MS: 283 (62, Mþ), 282 (100), 204 (4), 156
(4), 133 (8). HR-EI-MS: 283.13699 (Mþ, C21H17Nþ; calc. 283.13610).
3,5-Bis[(E)-2-(4-methylphenyl)ethenyl]pyridine (5h). White solid (236 mg, 76%). M.p. 118 – 1198.
IR: 3038m, 3020m, 2998m, 2912m, 2854m, 2725m, 1603w, 1583w, 1510w, 1462w, 1434w, 1414w, 1371w,
1327w, 1303w, 1241w, 1212w, 1180w, 1112w, 1041w, 1017w, 966s, 950m, 889w, 849m, 841m, 799s, 667w,
626w. 1H-NMR (300 MHz): 2.30 (s, 2 Me); 6.93 (d, J ¼ 16.1, 2 CH); 7.09 – 7.14 (m, 6 H); 7.37 (d, J ¼ 8.1, 4
arom. H); 7.85 (br. s, 1 arom. H); 8.50 (s, 2 arom. H). 13C-NMR (75 MHz): 21.3 (Me); 123.6, 126.7, 129.4,

Helvetica Chimica Acta – Vol. 93 (2010)
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129.6, 131.1 (CH); 133.2, 133.8, 138.3 (C); 146.6 (CH). GC/EI-MS: 311 (72, Mþ), 310 (100), 294 (10), 170
(6), 154 (12). HR-EI-MS: 310.15921 ([M ꢀ 1]þ, C23H20Nþ; calc. 310.15957).
Dibutyl 3,3’-[2,2’-Bipyridine]-5,5’-diylbis[(E)-prop-2-enoate] (7a). White solid (169 mg, 83%). M.p.
225 – 2278. IR: 3055w, 2957w, 2933w, 2872w, 1714s, 1635s, 1469s, 1377s, 1303s, 1250m, 1200m, 1168s, 1140s,
1
1117s, 1056m, 1020m, 989m, 976m, 953m, 925m, 900m, 862m, 833s, 723m, 707m, 652m, 532m. H-NMR
(250 MHz): 0.86 (t, J ¼ 7.3, 2 Me); 1.33 – 1.45 (m, 2 CH2); 1.57 – 1.69 (m, 2 CH2); 4.18 (t, J ¼ 6.7, 2 CH2O);
6.45 (d, J ¼ 15.2, 2 CH); 7.61 (d, J ¼ 15.2, 2 CH); 7.88 (dd, J ¼ 2.2, 8.4, 2 arom. H); 8.39 (d, J ¼ 8.3, 2 arom.
H); 8.70 (d, J ¼ 1.9, 2 arom. H). 13C-NMR (62.9 MHz): 13.6 (Me); 19.2, 29.7 (CH2); 64.7 (CH2O); 120.6,
121.3 (CH); 130.5 (C); 135.0, 140.0, 149.4 (CH); 156.4, 166.4 (C). GC/EI-MS: 408 (100, Mþ), 363 (24),
336 (65), 279 (70), 178 (11). HR-EI-MS: 408.20450 (Mþ, C24H28N2O4þ ; calc. 408.20491).
Dihexyl 3,3’-[2,2’-Bipyridine]-5,5’-diylbis[(E)-prop-2-enoate] (7b). White solid (329 mg, 71%). M.p.
215 – 2178. IR: 2952m, 2928m, 2870m, 1714s, 1635s, 1592w,1544w, 1468m, 1376m, 1304s, 1273w, 1250w,
1214w, 1199w, 1171s, 1139s, 1067w, 1013w, 990m, 975m, 931w, 899w, 879w, 863w, 834m, 815w, 724m, 708m,
1
652m, 599w, 538w, 529w. H-NMR (300 MHz): 0.83 (t, J ¼ 6.6, 2 Me); 1.17 – 1.35 (m, 6 CH2); 1.59 – 1.69
(m, 2 CH2); 4.15 (t, J ¼ 6.7, 2 CH2O); 6.49 (d, J ¼ 15.2, 2 CH); 7.63 (d, J ¼ 15.2, 2 CH); 7.89 (d, J ¼ 8.3, 2
arom. H); 8.40 (d, J ¼ 8.3, 2 arom. H); 8.70 (br. s, 2 arom. H). 13C-NMR (75.5 MHz): 13.9 (Me); 22.5,
25.6, 28.6, 31.4 (CH2); 65.0 (CH2O); 120.6, 121.3 (CH); 130.5 (C); 135.0, 140.4, 149.3 (CH); 156.3 (C);
166.4 (C¼O). GC/EI-MS: 464 (73, Mþ), 407 (17), 363 (100), 336 (91), 324 (34), 279 (65), 205 (14), 57
(13). HR-EI-MS: 464.27481 (Mþ, C28H36N2O4þ ; calc. 464.26751).
Bis(2-ethylhexyl) 3,3’-[2,2’-Bipyridine]-5,5’-diylbis[(E)-prop-2-enoate] (7c). White solid (213 mg,
82%). M.p. 255 – 2578. IR: 2957s, 2926s, 2858s, 1709s, 1633s, 1568m, 1468m, 1379m, 1302s, 1254m, 1162s,
1135m, 1050m, 1005w, 839m, 767w, 748w, 729w, 709w, 546w. 1H-NMR (250 MHz): 0.82 – 0.90 (m, 4 Me);
1.18 – 1.39 (m, 8 CH2); 1.59 – 1.69 (m, 2 CH); 4.08 – 4.10 (m, 2 CH2O); 6.51 (d, J ¼ 15.2, 2 CH); 7.64 (d,
J ¼ 15.2, 2 CH); 7.91 (dd, J ¼ 2.2, 8.4, 2 arom. H); 8.39 (d, J ¼ 8.3, 2 arom. H); 8.72 (br. s, 2 arom. H).
13C-NMR (62.9 MHz): 11.0, 14.0 (Me); 23.0, 23.8, 28.9, 30.4 (CH2); 38.8 (CH); 67.2 (CH2O); 120.6, 121.3
(CH); 130.5 (C); 135.0, 140.4, 149.4 (CH); 156.4 (C); 166.5 (C¼O). GC/EI-MS: 520 (21, Mþ), 491 (6),
408 (14), 391 (37), 364 (22), 296 (100), 205 (7). HR-EI-MS: 520.33045 (Mþ, C32H44N2O4þ ; calc.
520.33011).
Di(tert-butyl) 3,3’-[2,2’-Bipyridine]-5,5’-diylbis[(E)-prop-2-enoate] (7d; see also Fig. 3)1). White
solid (342 mg, 84%). M.p. 237 – 2388. IR: 3006w, 2976w, 2928w, 2855w, 1699s, 1667w, 1634m, 1555w,
1544w, 1468m, 1455m, 1363m, 1315m, 1251m, 1208m, 1146s, 1054m, 1023m, 993s, 981s, 835s, 765m, 750m,
738m, 710m, 650m, 589w. 1H-NMR (300 MHz): 1.47 (s, 6 Me); 6.43 (d, J ¼ 15.2, 2 CH); 7.56 (d, J ¼ 15.2,
2 CH); 7.89 (dd, J ¼ 2.2, 8.4, 2 arom. H); 8.39 (d, J ¼ 8.3, 2 arom. H); 8.71 (d, J ¼ 2.0, 2 arom. H).
13C-NMR (75.5 MHz): 28.2 (Me); 81.0 (C); 121.3, 122.5 (CH); 130.7 (C); 135.0, 139.3, 149.2 (CH); 156.1
(C); 156.5 (C¼O). GC/EI-MS: 408 (24, Mþ), 352 (27), 296 (100), 205 (10), 279 (40), 252 (80), 205 (10).
HR-EI-MS: 408.20549 (Mþ, C24H28N2O4þ ; calc. 408.20491).
Bis(2-methylpropyl) 3,3’-[2,2’-Bipyridine]-5,5’-diylbis[(E)-prop-2-enoate] (7e). White solid
(314 mg, 77%). M.p. 231 – 2328. IR: 2959m, 2929m, 2873m, 1728s, 1679w, 1641w, 1632w, 1590w, 1462m,
1378m, 1235s, 1169 s, 1092m, 984m, 945m, 800m, 784m, 648w. 1H-NMR (300 MHz): 0.93 (d, J ¼ 6.7,
4 Me); 1.89 – 1.97 (m, 2 CH); 3.94 (d, J ¼ 6.7, 2 CH2O); 6.53 (d, J ¼ 15.2, 2 CH); 7.65 (d, J ¼ 15.2, 2 CH);
7.91 (d, J ¼ 2.1, 8.4, 2 arom. H); 8.39 (d, J ¼ 8.3, 2 arom. H); 8.33 (br. s, 2 arom. H). 13C-NMR (62.9 MHz):
18.1 (Me); 26.8 (CH); 69.9 (CH2O); 119.6, 120.3 (CH); 129.5 (C); 134.0, 139.5, 148.4 (CH); 155.4 (C);
165.4 (C¼O). GC/EI-MS: 408 (56, Mþ), 352 (17), 296 (100), 205(11), 131 (6). HR-EI-MS: 408.20451
(Mþ, C24H28N2Oþ4 ; calc. 408.20491).
Financial support by the State of Mecklenburg-Vorpommern (Landesgraduiertenstipendium for
M. H.), by the State of Pakistan (HEC scholarships for M. H. and I. M.), by the DAAD (scholarships for
A. A. and I. M.), and by the Friedrich-Irgard-Harms-Stiftung (scholarship for A. A.) is gratefully
acknowledged.

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Received March 18, 2010