Notes
BENA 1b was synthesized according to a modified literature
J . Org. Chem., Vol. 66, No. 9, 2001 3199
(ddd, J ) 6.6, 8.5, 14.5, 1H), 3.72 (s, 3H), 3.73 (s, 3H), 3.81 (dd,
J ) 6.6, 9.8, 1H), 4.31-4.46 (m, 1H), 6.81, 6.82, 7.10, 7.12 (4d,
J ) 8.5, 8H). 13C NMR (62.9 MHz, CDCl3): δ ) 19.5, 41.2, 46.0,
55.2, 81.7, 114.0, 114.1, 128.3, 128.7, 135.1, 135.4, 158.2, 158.3.
14N NMR (21.7 MHz, CDCl3): δ ) 14.9, ∆ν1/2 ) 470 Hz (NO2).
IR (KBr, cm-1): 2996, 2935, 2836, 1609, 1548, 1510, 1460, 1389,
1357, 1302, 1249, 1177, 1033, 827. Anal. Calcd for C18H21NO4
(315.37): C 68.55, H 6.71, N 4.44. Found: C 68.64, H 6.89, N
4.81.
procedure.1b To a solution of 2-nitropropane (135 µL, 1.5 mmol)
and NEt3 (0.52 mL, 3.75 mmol) in CH2Cl2 (2 mL) at 0 °C was
added tert-butyldimethylsilyl triflate (0.76 mL, 3.3 mmol), and
the mixture was stirred for 3 h at 0 °C. A solution of citric acid
(0.20 g, 1.0 mmol) and NEt3 (0.83 mL, 6.0 mmol) in CH2Cl2 (2
mL) was rapidly injected. After 1 min, the mixture was diluted
with petroleum ether (7 mL) and poured into H2O (15 mL)/
petroleum ether (15 mL). The organic phase was washed with
water (10 mL), saturated aqueous NaHCO3 (10 mL), water (10
mL), aqueous NaHSO4‚H2O (800 mg in 90 mL of water), water
(10 mL), and brine (10 mL) and dried (Na2SO4). Concentration
in vacuo afforded 440 mg (ca. 90%) as a clear colorless oil
containing 5-10% of Me2-t-BuSiOH which can be removed by
distillation. Bp 85-95 °C/0.03 Torr (Kugelrohr).
6,6-Bis(p-m eth oxyp h en yl)-4-n itr oh exa n oic a cid m eth yl
ester was obtained from 1c (0.55 mmol) and 2f-OSiMe3 (0.50
mmol) by the same procedure in 69% yield. Column chromatog-
raphy: petroleum ether:ethyl acetate ) 8:1, Rf(petroleum ether:
ethyl acetate ) 3:1) ) 0.22. Bp 205-210 °C (bath temperature)/
1
0.09 Torr. H NMR (300 MHz, CDCl3): δ ) 2.05-2.41 (m, 5H),
BENA 1d . Bromotrimethylsilane (0.58 mL, 4.4 mmol) was
added to a solution of 1-phenylnitroethane (302 mg, 2.0 mmol)
and NEt3 (0.64 mL, 4.6 mmol) in CH2Cl2 (1.3 mL) at 0 °C, and
the reaction mixture was kept at this temperature for 42 h. Then
the mixture was diluted with petroleum ether (3 mL) and poured
into H2O (10 mL)/petroleum ether (5 mL). The organic phase
was washed with aqueous NaHSO4‚H2O (57 mg in 10 mL of
water), water (2 × 10 mL), and brine (10 mL) and dried (Na2-
SO4). Concentration in vacuo afforded 520 mg (88%) of 1d as a
clear colorless oil. Bp 120-125 °C (Kugelrohr)/0.038 Torr. 1H
NMR (300 MHz, CDCl3) δ ) 0.16 (s, 18H), 4.91 (s, 1H), 5.40 (s,
1H), 7.30-7.34 (m, 3H), 7.45-7.51 (m, 2H). 13C NMR (75.5 MHz,
CDCl3): δ ) 0.1, 103.0, 127.8, 128.13, 128.07, 137.0, 159.1. 29Si
NMR (59.6 MHz, CDCl3): δ ) 24.6 (SiMe3). Anal. Calcd for
C14H25NO2Si2 (295.53): C 56.90, H 8.53, N 4.74. Found: C 56.76,
H 8.70, N 4.80.
2.69 (ddd, J ) 5.9, 9.6, 14.7, 1H), 3.62 (s, 3H), 3.74 (s, 3H), 3.76
(s, 3H), 3.80 (dd, J ) 5.9, 10.7, 1H), 4.30-4.43 (m, 1H), 6.80,
6.84, 7.09, 7.10 (4d, J ) 8.8, 8H). 13C NMR (75.5 MHz, CDCl3):
δ ) 28.9, 29.9, 39.9, 46.0, 51.8, 55.2, 85.9, 114.0, 114.2, 128.2,
128.7, 134.6, 135.5, 158.2, 158.4, 172.0 (CdO). 14N NMR (21.7
MHz, CDCl3): δ ) 12.9, ∆ν1/2 ) 580 Hz (NO2). IR (KBr, cm-1):
2954, 2837, 1737, 1610, 1584, 1549, 1510, 1440, 1303, 1249,
1178, 1033, 830. Anal. Calcd for C21H25NO6 (387.44): C 65.10,
H 6.50, N 3.62. Found: C 65.16, H 6.34, N 3.48.
4,4-Bis(2,3-d ih yd r oben zofu r a n -5-yl)-2-n itr obu ta n e. TM-
SOTf (114 µL, 0.60 mmol) was added to a solution of 2e-OSiMe3
(170 mg, 0.50 mmol) and 2,6-di-tert-butylpyridine (19 mg, 0.093
mmol) in CH2Cl2 (1.5 mL) at -60 °C. Then, a solution of BENA
1a (140 mg, 0.60 mmol) in CH2Cl2 (1.5 mL) was added. After
stirring for 15 min at -60 °C, the reaction mixture was quenched
with a solution of BnNEt3Cl (159 mg, 0.70 mmol) in CH2Cl2 (1.5
mL), kept for another 5 min at -60 °C, and treated with a
mixture of AcOH (57 µL, 1.00 mmol) and NEt3 (153 µL, 1.10
mmol) dissolved in CH2Cl2 (1.5 mL) followed by addition of AcOH
(57 µL, 1.00 mmol) in MeOH (1.5 mL). The cooling bath was
removed, and the reaction mixture was allowed to warm to room
temperature and kept at that temperature an for additional 1
h. For the workup, the mixture was poured into H2O (10 mL)/
Et2O (20 mL). The organic phase was separated, and the aqueous
phase was extracted with Et2O (3 × 10 mL). The combined
organic extracts were washed with brine (10 mL), dried (Na2-
SO4), and concentrated in vacuo. Flash column chromatography
(petroleum ether:ethyl acetate ) 8:1) afforded 36 mg of colorless
oil (21%). Rf(petroleum ether:ethyl acetate ) 3:1) ) 0.33. 1H
NMR (300 MHz, CDCl3): δ ) 1.53 (d, J ) 6.6, 3H), 2.28 (ddd,
J ) 5.2, 9.6, 14.5, 1H), 2.73 (ddd, J ) 6.5, 8.5, 14.5, 1H), 3.15
(td, J ) 2.7, 8.5, 4H), 3.78 (dd, J ) 6.5, 9.6, 1H), 4.36-4.48 (m,
1H), 4.53 (td, J ) 2.7, 8.5, 4H), 6.70 (d, J ) 8.2, 1H), 6.71 (d,
J ) 8.2, 1H), 6.91-7.04 (m, 4H). 13C NMR (75.5 MHz, CDCl3):
δ ) 19.6, 29.7, 41.5, 46.5, 71.2, 81.7, 109.1, 109.3, 123.9, 124.3,
126.8, 127.1, 127.5, 127.6, 135.2, 135.5, 158.8, 158.9. IR (film,
cm-1): 2959, 2922, 2896, 1613, 1549, 1491, 1443, 1390, 1358,
1240, 1107, 983, 943, 818, 737. MS (EI): m/z (%) ) 339 (14) [M+],
292 (11), 264 (14), 252 (20), 251 (100) [2e].
Bis(p-m eth oxyp h en yl)m eth yl Tr im eth ylsilyl Eth er (2f-
OSiMe3).14 To a solution of bis(p-methoxyphenyl)methanol (0.78
g, 3.2 mmol) and NEt3 (0.58 mL, 4.16 mmol) in benzene (6 mL)
at room temperature was added chlorotrimethylsilane (0.49 mL,
3.8 mmol), and the mixture was stirred at room temperature
for 7 h. The reaction mixture was diluted with benzene and
filtered, and the volatile components were evaporated. The
residue was diluted with benzene, filtered, and concentrated in
vacuo to give 886 mg (88%) 2f-OSiMe3 as a clear colorless oil.
Bp 125-130 °C (bath temperature)/ 0.08 Torr, Rf(petroleum
ether:ethyl acetate ) 3:1) ) 0.51. 1H NMR (250 MHz, CDCl3):
δ ) 0.06 (s, 9H), 3.77 (s, 6H), 5.69 (s, 1H), 6.82, 7.22 (2d, J )
8.5, 8H). 13C NMR (75.5 MHz, CDCl3): δ ) 0.2, 55.1, 75.6, 113.4,
127.6, 137.3, 158.5. 29Si NMR (59.6 MHz, CDCl3): δ ) 17.80
(SiMe3). IR (KBr, cm-1): 2955, 1611, 1511, 1302, 1249, 1171,
1073, 1037, 890, 841. Anal. Calcd for C18H24O3Si (316.48): C
68.31, H 7.64. Found: C 68.25, H 7.53.
4,4-Bis(p -m et h oxyp h en yl)-2-n it r obu t a n e. TMSOTf (114
µL, 0.60 mmol) was added to a solution of 2f-OSiMe3 (158 mg,
0.51 mmol) and 2,6-di-tert-butyl-4-methylpyridine (5.1 mg, 0.025
mmol) in CH2Cl2 (1 mL) at -78 °C. Then, a solution of BENA
1a (0.55 mmol) in CH2Cl2 (1 mL) was added. After stirring for
15 min at -78 °C, the reaction mixture was quenched with a
solution of BnNEt3Cl (159 mg, 0.70 mmol) in CH2Cl2 (1 mL),
kept for another 5 min at -78 °C, and treated with a mixture of
AcOH (57 µL, 1.00 mmol) and NEt3 (153 µL, 1.10 mmol)
dissolved in CH2Cl2 (1 mL) followed by addition of AcOH (57
µL, 1.00 mmol) in MeOH (1 mL). The cooling bath was removed,
and the reaction mixture was allowed to warm to room temper-
ature and kept at that temperature for an additional 1 h. For
the workup, the mixture was poured into H2O (10 mL)/Et2O (20
mL). The organic phase was separated, and the aqueous phase
was extracted with Et2O (3 × 10 mL). The combined organic
extracts were washed with brine (10 mL), dried (Na2SO4), and
concentrated in vacuo. Flash column chromatography (petroleum
ether:ethyl acetate ) 6:1) afforded 129 mg of a colorless oil (82%).
Rf(petroleum ether:ethyl acetate ) 3:1) ) 0.41. Bp 140-150 °C
4-F er r ocen yl-4-p h en yl-2-n itr obu ta n e. TMSOTf (57 µL,
0.30 mmol) was added to a solution of 2d -OAc (0.10 g, 0.31 mmol)
and 2,6-di-tert-butylpyridine (11.5 mg, 0.060 mmol) in CH2Cl2
(2 mL) at -78 °C. Then, a solution of BENA 1a (or 1b) (0.45
mmol) in CH2Cl2 (2 mL) was added. After stirring for 32 h at
-78 °C (or 38 h for 1b), the reaction mixture was quenched with
a solution of BnNEt3Cl (96 mg, 0.42 mmol) in CH2Cl2 (1.5 mL),
kept for another 5 min at -78 °C, and treated with a mixture of
AcOH (52 µL, 0.90 mmol) and NEt3 (167 µL, 1.20 mmol)
dissolved in CH2Cl2 (1.5 mL) followed by addition of AcOH (52
µL, 0.90 mmol) in MeOH (2 mL). The cooling bath was removed,
and the reaction mixture was allowed to warm to room temper-
ature and kept for an additional 1 h. For the workup, the mixture
was poured into H2O (10 mL)/Et2O (20 mL). The organic phase
was separated, and the aqueous phase was extracted with Et2O
(3 × 10 mL). The combined organic extracts were washed with
brine (10 mL), dried (Na2SO4), and concentrated in vacuo. Flash
column chromatography on silica gel (petroleum ether:ethyl
acetate ) 20:1) afforded the product as a yellow oil in 31% yield
from BENA 1a , 40% yield from BENA 1b. Two isomers in the
ratio 2:1. Rf(petroleum ether:ethyl acetate ) 10:1) ) 0.34. 1H
1
(bath temperature)/0.03 Torr. H NMR (250 MHz, CDCl3): δ )
1.49 (d, J ) 7.2, 3H), 2.28 (ddd, J ) 5.3, 9.8, 14.5, 1H), 2.73
(14) For recent reports on the synthesis of trimethylsilyl ethers,
see: (a) Gautret, P.; El-Ghammarti, S.; Legrand, A.; Couturier, D.;
Rigo, B. Synth. Commun. 1996, 26, 707-713. (b) Karimi, B.; Golshani,
B. J . Org. Chem. 2000, 65, 7228-7230.