È
T. Renouard, M. Gratzel / Tetrahedron 57 ,2001) 8145±8150
8149
4.1.2. 6,60-Dicyano-4,40-bis,ethoxycarbonyl)-2,20-bipyri-
dine ,3). A solution of freshly distilled dimethyl sulfate
&5 mL) and 4,40-bisðoxycarbonyl)-2,20-bipyridine-N,N0-
dioxide 2 &0.66 g, 2.0 mmol) was warmed at 1008C for
4 h. After cooling to room temperature, the viscous yellow
mixture was added dropwise to a rapidly stirred, cooled
&2108C) and saturated aqueous potassium cyanide solution
&25 mL). A fawn colored solid developed during the course
of the addition. Stirring was continued at 2108C for 4 h and
the reaction mixture was placed at 2208C overnight. Then,
the brownish precipitate was ®ltered, washed with water
&2£10 mL) and dried under vaccuum. Using this precipitate,
the same reaction was repeated once more. The resulting
solid was dissolved in the smallest amount of dichloro-
methane, ®ltered and made precipitate by slow addition to
methanol &50 mL) to yield the title compound as a white
powder &0.38 g, 55%). 1H NMR &CDCl3, d ppm, J Hz): 9.20
&6H, t, CH3, J6.8 Hz). Anal. found: C, 71.00; H, 5.42%.
Calcd for C24H22O6: C, 70.93; H, 5.45%.
4.1.6.
N-{2-oxo-2-[2-,4-tert-butyl)pyridyl]ethyl}pyri-
dinium iodide ,6b). 2-Acetyl-4-tert-butylpyridine &1.6 g,
9.0 mmol) was added to a solution of iodine &5.0 g,
20 mmol) in anhydrous pyridine &20 mL) and the mixture
was heated at 708C for 1 h. The dark solution was cooled to
room temperature and the solvent was evaporated. To the
resulting mixture was added dichloromethane &20 mL).
After ®ltration and evaporation, the title compound was
collected as ®ne brownish crystals &0.94 g, 66%). 1H
0
0
NMR &CDCl3, d ppm, J Hz): 9.01 &2H, d, H2 ,6 , J
6.6 Hz); 8.78 &1H, dd, H6, J5.1,0 0.55 Hz); 8.28 &2H, d,
0
0
H
3 ,5 , J6.6 Hz); 8.15 &1H, d, H4 , J7.7 Hz); 8.02 &1H,
dd, H3, J1.2, 0.55 Hz); 7.85 &1H, dd, H5, J5.1, 1.2 Hz);
1.34 &9H, s, tBu). Anal. found: C, 48.14; H, 4.88; N, 7.02%.
Calcd for C16H19N2OI.H2O: C, 48.01; H, 5.28; N, 6.99%.
0
0
&2H, d, H3,3 , J1.4 Hz); 8.36 &2H, d, H5,5 , J1.4 Hz); 4.55
&4H, q, CH2, J7.1 Hz); 1.50 &6H, t, CH3, J7.1 Hz). Anal.
found: C, 61.79; H, 4.10; N, 15.85%. Calcd for C18H14N4O4:
C, 61.71; H, 4.03; N, 15.99%.
4.1.7. 40,400-Bis[p-,methoxycarbonyl)phenyl]-2,20:60,200:
600,2000-quaterpyridine ,7a). 1,6-bis[p-&methoxycarbonyl)-
phenyl]hexa-1,5-diene-3,4-dione 5-Me &0.19 g, 0.5 mmol),
N-[2-oxo-2-&2-pyridyl)ethyl]pyridinium iodide 6a &0.33 g,
1.0 mmol) and ammonium acetate &1.0 g, 13 mmol) were
re¯uxed in ethanol &25 mL) for 12 h. The mixture was
cooled to room temperature and the precipitate that formed
was ®ltered and washed with ethanol &2£5 mL) to yield the
title compound as an off-white solid &0.01 0g0 , 34%). 1H NMR
&CDCl3, d ppm, J Hz): 8.98 &2H, d, H3 ,5 , J1.6 Hz); 8.82
4.1.3. 6,60-Bis,1-H-benzimidazol-2-yl)-4,40-bis,methoxy-
carbonyl)-2,20-bipyridine ,4). Sodium methylate &62 mg,
1.0 mmol) and 6,60-dicyano-4,40-bisðoxycarbonyl)-2,20-
bipyridine 3 &175 mg, 0.5 mmol) were heated at 608C in
freshly distilled methanol &40 mL) for 6 h. To this solution
was added o-phenylenediamine dihydrochloride &0.2 g,
1.0 mmol). The solution turned yellow followed by
formation of a precipitate. This mixture was stirred at
608C for 12 h. After cooling to room temperature, the
solution was treated with aqueous sodium carbonate
&20 mL). The precipitate was ®ltered and washed with
methanol &2£10 mL) to yield the title compound as an
0
00
000
&2H, d, H5 ,3 , J1.6 Hz); 8.77 &2H, d, H3,3 , J4.2 Hz);
000
8.73 &2H, d, H6,6 , J9.1 Hz); 8.26 &4H, d, Ar±H, J
8.4 Hz); 8.02 &4H, d, Ar±H, J8.4 Hz); 7.93 &2H, dd,
000
000
H4,4 , J7.7, 1.7 Hz); 7.41 &2H, dd, H5,5 , J6.5, 4.9 Hz);
4.01 &6H, s, CH3).
1
hygroscopic pale yellow powder &170 mg, 67%). H NMR
0
&DMSO-d6, d ppm, J Hz): 9.28 &2H, d, H3,3 , J1.4 Hz);
0
4.1.8.
40,400-Bis[p-,ethoxycarbonyl)phenyl]-2,20:60,200:
8.86 &2H, d, H5,5 , J1.4 Hz); 7.75 &4H, m, Ar±H); 7.31
600,2000-quaterpyridine ,7b). Using the same conditions as
for compound 7a, starting from 1,6-bis[p-ðoxycarbonyl)-
phenyl]hexa-1,5-diene-3,4-dione 5-Et &1.1 g, 2.7 mmol) the
title compound was obtained as a brownish powder &0.48 g,
&4H, m, Ar±H); 4.07 &6H, s, CH3). Anal. found: C, 60.28;
H, 4.65; N, 15.36%. Calcd for C28H20N6O4´3H2O: C, 60.21;
H, 4.69; N, 15.04%.
0
00
1
30%). H NMR &CDCl3, d pp0m0 , J Hz): 8.97 &2H, d, H3 ,5
,
0
4.1.4.
1,6-Bis[p-,methoxycarbonyl)phenyl]hexa-1,5-
J1.7 Hz); 8.82 &2H, d, H5 ,3 , J1.7 Hz); 8.77 &2H, ddd,
000
000
diene-3,4-dione ,5-Me). Piperidine &0.5 mL, 5.0 mmol)
and acetic acid &0.3 mL, 5.0 mmol) were added to a stirred
solution of methyl 4-formylbenzoate &1.55 g, 9.0 mmol) and
2,3-butanedione &0.4 mL, 4.5 mmol) in methanol &15 mL).
The mixture was re¯uxed for 6 h, while bright orange
crystals started to form. After cooling to room temperature,
the crystals were ®ltered and washed with methanol
&25 mL) to yield the title compound &0.42 g, 25%). 1H
NMR &DMSO-d6, d ppm, J Hz): 8.03 &4H, d, Ar±H, J
8.0 Hz); 7.95 &4H, d, Ar±H, J8.0 Hz); 7.84 &2H, d,
vCH, J16.0 Hz); 7.50 &2H, d, vCH, J16.0 Hz); 3.88
&6H, s, CH3).
H3,3 , J4.7, 1.6, 0.8 Hz); 8.72 &2H, dt, H6,6 , J7.9,
0.9 Hz); 8.26 &4H, d, Ar±H, J0008.6 Hz); 8.01 &4H, d, Ar±
H, J8.6 Hz); 7.93 &2H, dd, H4,4 , J7.8, 1.8 Hz); 7.41 &2H,
000
ddd, H5,5 , J7.5, 4.8, 1.2 Hz); 4.48 &4H, q, CH2, J
6.8 Hz); 1.48 &6H, t, CH3, J6.8 Hz). Anal. found: C,
75.19; H, 4.95; N, 9.30%. Calcd for C38H30N4O4: C,
75.23; H, 4.98; N, 9.26%.
4.1.9. 4,4000-Bis,tert-butyl)-40,400-bis[p-,methoxycarbonyl)-
phenyl]-2,20:60,200:600,2000-quaterpyridine ,7c). Using the
same conditions as for compound 7a, starting from 1,6-
bis[p-&methoxycarbonyl)phenyl]hexa-1,5-diene-3,4-dione
5-Me &1.65 g, 4.3 mmol) and N-{2-oxo-2-[2-&4-tert-butyl)-
pyridyl]ethyl}pyridinium iodide 6b &3.5 g, 9.2 mmol) the
title compound was obtained as a brownish powder
4.1.5. 1,6-Bis[p-,ethoxycarbonyl)phenyl]hexa-1,5-diene-
3,4-dione ,5-Et). Using the same conditions as for
compound 5-Me, starting from ethyl 4-formylbenzoate
&5.9 g, 33 mmol) the title compound was obtained as orange
crystals &1.13 g, 17%). 1H NMR &DMSO-d6, d ppm, J Hz):
8.02 &4H, d, Ar±H, J8.5 Hz); 7.95 &4H, d, Ar±H, J
8.5 Hz); 7.84 &2H, d, vCH, J16.3 Hz); 7.50 &2H, d,
vCH, J16.3 Hz); 4.35 &4H, q, CH2, J6.8 Hz); 1.34
1
&0.68 0g, 23%). H NMR &CDCl3, d ppm, J Hz) 9.06 &2H,
00
0
00
d, H3 ,5 , J1.6 Hz); 8.82 &2H, d, H5 ,3 , J1.6 Hz); 8.81
000
000
&2H, d, H3,3 , J1.4 Hz); 8.68 &2H, d, H6,6 , J5.3 Hz);
8.24 &4H, d, Ar±H, J8.5 Hz); 8.05 &4H, d, Ar±H, J
000
8.5 Hz); 7.42 &2H, dd, H5,5 , J5.3, 1.9 Hz); 4.00 &6H,
t
s, CH3); 1.49 &18H, s, Bu). Anal. found: C, 76.53; H,