8788 J. Am. Chem. Soc., Vol. 121, No. 38, 1999
Zhang and Tour
Hz, 4 H), 1.23 (m, 36 H), 0.85 (t, J ) 6.90 Hz, 6 H). 13C NMR (75
MHz, CDCl3) δ 201.15, 149.03, 142.36, 38.18, 31.92, 29.66, 29.64,
29.62, 29.49, 29.43, 29.35, 29.25, 23.71, 22.69, 14.12. HRMS Calcd
for C30H52N2O2: 472.4029. Found: 472.4018.
42 H), 0.74 (t, J ) 6.06 Hz, 6 H), 0.56 (s, 6 H). 13C NMR (100 MHz,
CDCl3) δ 153.80, 143.55, 100.38, 72.01, 41.86, 31.80, 29.94, 29.52,
29.42, 29.39, 29.24, 29.02, 28.15, 22.76, 22.57, 22.49, 21.99, 14.01.
HRMS Calcd for C40H72N2O4: 644.5492. Found: 644.5479.
2,5-Di(p-tert-butylbenzoyl)pyrazine (8c). To a slurry of 5 (4.10 g,
20.0 mmol) and anhydrous aluminum chloride (13.64 g, 100.00 mmol)
in dichloromethane (200 mL) at 0 °C was added dropwise tert-
butylbenzene (13.56 g, 100.00 mmol, neat) and the mixture was allowed
to warm to room temperature overnight. The reaction was quenched
with aqueous ammonium chloride at 0 °C and the mixture was filtered
through a pad of Celite. The organic phase was separated, and the
aqueous phase was extracted with dichloromethane. The combined
organic layers were washed with aqueous sodium bicarbonate and brine,
dried over magnesium sulfate, and filtered. The solvent was removed
in vacuo and the crude product was purified by flash chromatography
on silica gel (hexanes/dichloromethane/ethyl acetate, 3:2:1) followed
by recrystallization from hexanes/dichloromethane to afford 7.02 g
(88%) of the titled compound as yellow crystals. FTIR (KBr) 2958.3,
1657.8, 1607.1, 1468.3, 1405.5, 1352.0, 1267.8, 1176.0, 1106.9, 1029.3,
Diacetal 9c. See the procedure for 9a. 8c (2.00 g, 5.0 mmol),
neopentyl glycol (3.22 g, 30.0 mmol), benzene (40 mL), acetonitrile
(20 mL), and trifluoromethanesulfonic acid (40 mL) were used with
purification by chromatography on silica gel (hexanes/dichloromethane/
ethyl acetate, 3:2:1) to afford 2.82 g (98%) of the titled compound as
white crystals. FTIR (KBr) 2961.8, 2865.3, 1666.3, 1606.8, 1463.5,
1395.4, 1362.0, 1270.3, 1215.3, 1189.2, 1106.4, 1022.1, 982.3, 906.2,
1
830.0, 734.7, 671.5 cm-1. H NMR (400 MHz, CDCl3) δ 8.83 (s, 2
H), 7.47 (d, J ) 8.34 Hz, 4 H), 7.32 (d, J ) 8.30 Hz, 4 H), 3.66 (d, J
) 11.07 Hz, 4 H), 3.56 (d, J ) 11.01 Hz, 4 H), 1.26 (s, 18 H), 1.06 (s,
6 H), 0.80 (s, 6 H). 13C NMR (100 MHz, CDCl3) δ 154.6, 151.1, 141.8,
135.8, 126.8, 125.5, 99.7, 72.0, 34.5, 31.3, 30.2, 22.7, 22.2. HRMS
Calcd for C36H48N2O4: 572.3614. Found: 572.3623.
Diacetal 9d. See the procedure for 9a. 8d (1.10 g, 1.76 mmol),
neopentyl glycol (1.13 g, 10.56 mmol), benzene (16 mL), acetonitrile
(8 mL), and trifluoromethanesulfonic acid (50 µL) were used with
purification by chromatography on silica gel (hexanes/dichloromethane/
ethyl acetate, 8:2:1) to afford 1.31 g (93%) of the titled compound as
a white solid. FTIR (KBr) 2919.1, 2851.2, 1468.1, 1395.4, 1272.3,
1214.5, 1109.0, 1024.2, 980.1. 1H NMR (400 MHz, CDCl3) δ 8.85 (s,
2 H), 7.46 (d, J ) 8.14 Hz, 4 H), 7.13 (d, J ) 8.11 Hz, 4 H), 3.66 (d,
J ) 11.14 Hz, 4 H), 3.56 (d, J ) 11.10 Hz, 4 H), 2.54 (t, J ) 7.63 Hz,
4 H), 1.55 (p, J ) 7.56 Hz, 4 H), 1.24 (m, 36 H), 1.07 (s, 6 H), 0.86
(t, J ) 6.64 Hz, 6 H), 0.79 (s, 6 H). 13C NMR (100 MHz, CDCl3) δ
154.72, 143.10, 141.68, 135.98, 128.63, 127.11, 99.76, 72.0, 35.70,
31.94, 31.32, 30.24, 29.69, 29.66, 29.59, 29.52, 29.45, 29.38, 29.33,
22.72, 22.24, 22.09, 14.15. HRMS Calcd for C52H80N2O4: 796.6118.
Found: 796.6127.
1
953.1, 922.3, 843.9, 762.9, 705.5 cm-1. H NMR (400 MHz, CDCl3)
δ 9.26 (s, 2 H), 8.06 (d, J ) 8.59 Hz, 4 H), 7.54 (d, J ) 8.58 Hz, 4 H),
1.35 (s, 18 H). 13C NMR (100 MHz, CDCl3) δ 191.2, 157.9, 151.2,
143.9, 132.6, 131.0, 125.6, 35.3, 31.0. HRMS Calcd for C26H28N2O2:
400.2151. Found: 400.2143.
2,5-Di(p-n-dodecylbenzoyl)pyrazine (8d). See the procedure for
8c. 5 (2.05 g, 10.00 mmol), anhydrous aluminum chloride (6.82 g, 50.00
mmol), dichloromethane (100 mL), and 1-phenyldodecane (12.70 g,
50.00 mmol, neat) were used with purification by chromatography on
silica gel (hexanes/dichloromethane/ethyl acetate, 8:2:1) followed by
recrystallization from hexanes/dichloromethane to afford 2.68 g (43%)
of the titled compound as a yellow solid. FTIR (KBr) 2919.6, 2851.0,
1667.5, 1605.8, 1467.9, 1413.7, 1348.8, 1267.5, 1167.6, 1033.9, 941.1,
1
911.9, 849.3, 759.1, 710.6 cm-1. H NMR (400 MHz, CDCl3) δ 9.25
Diiododiacetal 10a. To n-butyllithium (27.8 mL, 42.0 mmol, 1.51
M in hexanes) was slowly added 2,2,6,6-tetramethylpiperidine (7.2 mL,
42.0 mmol) at 0 °C and the mixture was stirred at 0 °C for 30 min,
then cooled to -78 °C to form the LTMP solution. To the LTMP in
hexanes was added dropwise a solution of 9a (1.47 g, 3.50 mmol) in
ether/THF (5:1, 24.0 mL) at -78 °C. After being stirred at -78 °C for
15 min under argon, the mixture was warmed and stirred at -25 °C
for 4 h. Iodine (11.2 g, 44.0 mmol) in THF (50 mL) was added at -25
°C over 2 h via a syringe pump and the mixture was stirred at -25 °C
for an additional 2 h. The reaction was quenched with aqueous sodium
thiosulfate at -23 °C and allowed to warm to room temperature. The
organic phase was separated and the aqueous phase was extracted with
dichloromethane. The combined organic layers were washed with brine,
dried over magnesium sulfate, and filtered. The solvent was removed
in vacuo and the crude product was purified by chromatography on
silica gel (hexanes/ether, 5:1) followed by recrystallization from pentane
at -10 to 0 °C to afford 1.97 g (84%) of the titled compound as white
crystals. FTIR (KBr) 2959.2, 2865.5, 1470.0, 1396.3, 1268.2, 1179.9,
1117.1, 1082.7, 1061.5, 1037.3, 1009.4, 952.3, 921.9, 888.2. 1H NMR
(400 MHz, CDCl3) δ 3.49 (d, J ) 11.60 Hz, 4 H), 3.29 (d, J ) 11.23
Hz, 4 H), 1.95 (t, J ) 7.61 Hz, 4 H), 1.51 (p, J ) 7.60 Hz, 4 H), 1.28
(sext, J ) 7.37 Hz, 4 H), 1.25 (s, 6 H), 0.86 (t, J ) 7.24 Hz, 6 H), 0.62
(s, 6 H). 13C NMR (75 MHz, CDCl3) δ 154.7, 112.1, 100.3, 72.2, 40.0,
29.8, 24.5, 23.0, 22.7, 22.1, 14.1. HRMS Calcd for C24H38I2N2O4:
672.0921. Found: 672.0925. Anal. Calcd for C24H38I2N2O4: C, 42.87;
H, 5.70; N, 4.17. Found: C, 43.12; H, 5.75; N, 4.10.
(s, 2 H), 8.04 (d, J ) 8.15 Hz, 4 H), 7.31 (d, J ) 8.15 Hz, 4 H), 2.68
(t, J ) 7.59 Hz, 4 H), 1.64 (p, J ) 7.35 Hz, 4 H), 1.24 (m, 36 H), 0.86
(t, J ) 6.42 Hz, 6 H). 13C NMR (75 MHz, CDCl3) δ 191.2, 151.2,
150.0, 143.9, 132.8, 131.2, 128.6, 36.1, 31.9, 31.0, 29.7, 29.6, 29.5,
29.4, 29.3, 29.1, 28.8, 22.7, 14.1. HRMS Calcd for C42H60N2O2:
624.4655. Found: 624.4641.
Diacetal 9a. To 8a (0.98 g, 4.0 mmol) and neopentyl glycol (4.30
g, 40.0 mmol) in benzene (40 mL) and acetonitrile (20 mL) was added
trifluoromethanesulfonic acid (0.1 mL) and the mixture was heated to
reflux at 105-115 °C for 16 h.20 The reaction mixture was allowed to
cool to room temperature and poured into ice-cooled aqueous potassium
carbonate, and the resulting mixture was stirred while warming to room
temperature for 1 h. The organic phase was separated and the aqueous
phase was extracted with dichloromethane. The combined organic layers
were washed with brine, dried over magnesium sulfate, and filtered
through a pad of Celite. The solvent was removed in vacuo and the
crude product was purified by flash chromatography on silica gel
(hexanes/ether, 5:1) to afford 1.65 g (98%) of the titled compound as
a white solid. FTIR (KBr) 2952.9, 2865.8, 1467.2, 1364.2, 1242.9,
1
1176.3, 1113.2, 1079.2, 1016.9, 965.1, 926.0, 888.5. H NMR (300
MHz, CDCl3) δ 8.73 (s, 2 H), 3.50 (d, J ) 11.36 Hz, 4 H), 3.35 (d, J
) 11.15 Hz, 4 H), 1.79 (t, J ) 7.67 Hz, 4 H), 1.34 (m, 4 H), 1.19 (s,
6 H), 1.18 (m, 4 H), 0.77 (t, J ) 7.20 Hz, 6 H), 0.61 (s, 6 H). 13C
NMR (75 MHz, CDCl3) δ 153.9, 143.7, 100.5, 72.1, 41.7, 30.1, 24.8,
22.9, 22.7, 22.1, 14.0. HRMS Calcd for C24H40N2O4: 420.2988.
Found: 420.2979.
Diiododiacetal 10b. See the procedure for 10a. 2,2,6,6-Tetrameth-
ylpiperidine (5.1 mL, 30.0 mmol), n-butyllithium (20.7 mL, 30.0 mmol,
1.45 M in hexanes), 9b (0.97 g, 1.50 mmol) in ether/THF (2:1, 15
mL), and iodine (8.0 g, 31.5 mmol) in THF (40 mL) were used with
chromatography on silica gel (hexanes/dichloromethane/ethyl acetate,
8:2:1) followed by recrystallization from pentane at -10 to 0 °C to
afford 1.02 g (77%) of the titled compound. FTIR (KBr) 2923.0, 2854.0,
1465.5, 1266.4, 1178.9, 1084.9, 958.8. 1H NMR (400 MHz, CDCl3) δ
3.48 (d, J ) 11.48 Hz, 4 H), 3.28 (d, J ) 11.29 Hz, 4 H), 1.94 (t, J )
7.62 Hz, 4 H), 1.50 (m, 4 H), 1.25-1.21 (br m, 42 H), 0.85 (t, J )
6.47 Hz, 6 H), 0.62 (s, 6 H). 13C NMR (100 MHz, CDCl3) δ 154.76,
112.10, 100.30, 72.16, 40.24, 31.93, 29.81, 29.66, 29.60, 29.59, 29.55,
Diacetal 9b. See the procedure for 9a. 8b (1.89 g, 4.0 mmol),
neopentyl glycol (4.30 g, 40.0 mmol), benzene (40 mL), acetonitrile
(20 mL), and trifluoromethanesulfonic acid (0.1 mL) were used with
purification by chromatography on silica gel (hexanes/dichloromethane/
ethyl acetate, 8:2:1) to afford 2.48 g (96%) of the titled compound as
white crystals. FTIR (KBr) 2925.9, 2856.1, 1465.7, 1395.9, 1363.9,
1313.2, 1174.6, 1086.9, 1022.3, 977.3, 920.0. 1H NMR (400 MHz,
CDCl3) δ 8.68 (s 2 H), 3.45 (d, J ) 11.04 Hz, 4 H), 3.32 (d, J ) 11.15
Hz, 4 H), 1.74 (t, J ) 7.49 Hz, 4 H), 1.29 (m, 4 H), 1.13-1.09 (br m,
(20) Greene, T. W.; Wuts, P. G. M. ProtectiVe Groups in Organic
Synthesis, 2nd ed.; Wiley: New York, 1991.