Notes
J . Org. Chem., Vol. 62, No. 11, 1997 3769
pure product (3.2 g, 84% yield): mp 138-140 °C; TLC Rf ) 0.38
(80% ethyl acetate in hexane); IR (KBr) 3312, 3096, 1664, 1561,
1510, 1404, 1383, 1255, 1171, 1108, 830 cm-1; syn isomer 1H
NMR (DMSO-d6) δ 6.70 (d, 2H, J ) 8.83 Hz), 7.37 (d, 2H, J )
8.80 Hz), 8.15 (d, 1H, J ) 1.88 Hz), 9.26 (s, 1H); 13C NMR δ
115.1, 120.8, 129.9, 153.5, 158.7; UV-vis (acetonitrile) λmax 248
nm, ꢀ ) 2.1 × 104 anti isomer 1H NMR (DMSO-d6) δ 6.70 (d,
2H, J ) 8.83 Hz), 6.98 (d, 2H, J ) 8.71 Hz), 8.50 (d, 1H, J )
11.2 Hz), 9.85 (d, 1H, J ) 11.5 Hz); 13C NMR δ 115.7, 120.2,
129.6, 154.2, 162.4. The two isomers are in a 3:1 (syn:anti) ratio,
and assignments were based on the intensities of the NMR
peaks.20
N-F or m yl-4-(ter t-bu tyld im eth ylsiloxy)a n ilin e (2e). To a
stirred mixture of N-formyl-4-hydroxyaniline (1.2 g, 11.1 mmol)
in THF (50 mL) were added tert-butyldimethylsilyl chloride (2.0
g, 13.3 mmol) and triethylamine (1.9 mL, 13.3 mmol), and the
mixture was held at 0 °C in an ice bath. The reaction mixture
was stirred under a nitrogen atmosphere while it warmed to
room temperature and stirring was continued overnight. TLC
analysis (70% ethyl acetate in hexane) showed complete disap-
pearance of the starting phenol and the appearance of a new
spot. Removal of the solvent by rotary evaporation, followed by
column chromatography (50% ethyl acetate in hexane), afforded
the desired N-formyl-4-(tert-butyldimethylsiloxy)aniline as a
colorless oil (2.6 g, 93% yield): TLC Rf ) 0.43 (70% ethyl acetate
in hexane); IR (neat) 3278, 3122, 3056, 2945, 2856, 1678, 1600,
1511, 1472, 1406, 1250, 1167, 911, 833, 778 cm-1; syn isomer
1H NMR (CDCl3) δ 0.18 (d, 6H, J ) 4.0 Hz), 0.98 (d, 9H, J ) 2.3
Hz), 6.78-6.83 (t, 1H), 7.40 (d, 2H, J ) 6.7 Hz), 7.53 (s, 1H),
8.30 (d, 1H, J ) 1.9 Hz), 8.38 (s, 1H); anti isomer 1H NMR
(CDCl3) δ 0.17 (d, 6H J ) 4.0 Hz), 0.97 (d, 9H, J ) 2.3 Hz),
6.78-6.83 (d, 1H), 6.98 (d, 1H, J ) 6.6 Hz), 7.53 (br, 1H), 8.15
(d, 2H, J ) 11.0 Hz), 8.53 (d, 2H, J ) 11.5 Hz); 13C NMR δ 115.7,
120.2, 129.6, 154.2, 162.4; (syn and anti) 13C NMR δ -4.5, 18.2,
25.6, 120.4, 121.0, 121.4, 130.1, 130.5, 152.8, 153.7, 158.7, 162.9.
The two isomers are in a 1:1 ratio and could be distinguished in
the 1H spectrum using saturation transfer techniques.
4-(ter t-Bu tyld im eth ylsiloxy)p h en yl Isocya n id e (3e). To
a stirred solution of N-formyl-4-(tert-butyldimethylsiloxy)aniline
(2.1 g, 8.0 mmol) in dichloromethane (50 mL) were added the
components triethylamine (1.2 g, 12 mmol), carbon tetrachloride
(1.8 g, 12 mmol), and triphenylphosphine (3.1 g, 12 mmol), and
the mixture was held at 0 °C in an ice bath. The reaction
mixture was stirred under a nitrogen atmosphere while it
warmed to room temperature and stirring was continued for 5
h. TLC analysis (70% ethyl acetate in hexane) showed complete
disappearance of the starting formamide and the appearance of
a new spot. Removal of the solvent by rotary evaporation
followed by column chromatography (40% ethyl acetate in
hexane) afforded the desired 4-(tert-butyldimethylsiloxy)phenyl
isocyanide as a colorless oil (1.6 g, 83% yield): TLC Rf ) 0.48
(70% ethyl acetate in hexane); IR (neat) 2956, 2123, 1602, 1504,
1472, 1272, 909, 839, 778 cm-1; 1H NMR (CDCl3) δ 0.21 (s, 6H),
0.98 (s, 9H), 6.81 (dd, 2H, J ) 6.7 and 6.7 Hz), 7.27 (d, 2H, J )
7.3 Hz); 13C NMR δ -4.5, 18.2, 25.6, 120.0, 120.7, 127.7, 156.5,
163.2. Anal. Calcd: C, 66.95; H, 8.15; N, 6.00. Found: C, 66.75;
H, 7.96; N, 5.85.
of 4-(tert-butyldimethylsiloxy)phenyl isocyanide (0.23 g, 1.0
mmol) in THF (5.0 mL) and held at 0 °C in an ice bath. The
reaction mixture was stirred under a nitrogen atmosphere for
15 min. TLC analysis (30% ethyl acetate in hexane) showed
complete disappearance of the starting silyl ether and the
appearance of a new spot. Removal of the solvent by rotary
evaporation followed by column chromatography (20% ethyl
acetate in hexane) afforded the desired 4-hydroxyphenyl iso-
cyanide as a colorless oil (0.12 g, 97% yield): TLC Rf ) 0.42 (30%
ethyl acetate in hexane); IR (neat) 3278, 2124, 1610, 1594, 1508,
1448, 1369, 1280, 1225, 1189, 1161, 1102, 1066, 967, 928, 839
1
cm-1; H NMR (CDCl3) δ 6.84 (d, 2H, J ) 8.8 Hz), 7.25 (d, 2H,
J ) 8.7 Hz); 13C NMR δ 116.5, 119.4, 128.2, 156.9, 161.5. Anal.
Calcd: C, 70.60, H, 4.20; N, 11.80. Found: C, 69.96; H, 4.75;
N, 11.36 (the elemental analysis is slightly off due to oxidation
during the delay caused by transportation).
P oly((4-h yd r oxyp h en yl)im in om et h ylen e). To a stirred
solution of anhydrous NiCl2 (3.0 mg) in methyl alcohol (5.0 mL)
was added 4-hydroxyphenyl isocyanide (0.22 g, 1.8 mmol) slowly.
The reaction mixture was stirred at room temperature for 7 days.
The polymerization was followed by observing the disappearance
of the isocyanide by TLC and in the IR spectrum of the reaction
mixture. The precipitates were isolated by suction filtration.
After washing thoroughly with methyl alcohol, the resulting
polymer, poly((4-hydroxyphenyl)iminomethylene), was dried in
vacuo to give a black solid (165 mg, 75% yield): mp 340-342 °C
(dec); IR (KBr) 3411, 1604, 1500, 1439, 1361, 1228, 1150, 1094,
1006, 828 cm-1; UV-vis (dichloromethane) λmax 416 nm; 1H NMR
(DMSO-d6) δ 6.5 (br, 4H), 9.3 (br, 1H).
P oly(im in om eth ylen eoxy-1,4-p h en ylen e). 4-Hydroxyphe-
nyl isocyanide (0.36 g, 3.0 mmol) was added slowly to chloroform
(5 mL) and the reaction mixture was stirred at room temperature
for 14 days. The polymerization was followed by observing the
disappearance of the isocyanide by TLC and in the IR spectrum
of the reaction mixture. The precipitates were isolated by
suction filtration. After washing thoroughly with chloroform,
the resulting polymer, d(CHO-æ-NdCHO-æ-N)nd, was dried in
vacuo to give a black solid (230 mg, 63% yield). This black solid
could be partially purified in the following manner: dissolution
in glyme yields a deep red solution which can easily be filtered
to remove some black, gummy material. Reprecipitation with
hexane separates a dark solid which can be washed with ethyl
acetate until the washings are no longer yellow. Any trapped
ethyl acetate can be removed from this powdery dark solid by
washing with hexane. Spectral analysis clearly indicates that
this powder is not a single material: mp 260-269 °C (dec); IR
(KBr) 3379, 2948, 1670, 1617, 1513, 1457, 1384, 1226, 833, cm-1
;
1H NMR (DMSO-d6) δ 6.6 (br, 2.6H), 7.2 (br, 2.1H), 9.1 (br, 1.0H)
(the first two broad resonances overlap).
Ack n ow led gm en t . We wish to thank Michael
MacGregor for the production of most of the NMR
spectra utilized in this study. This research was sup-
ported by the U.S. Army Research Office, grant number
DAAL03-92-G-0391.
4-Hyd r oxyp h en yl Isocya n id e (3k ). Tetrabutylammonium
fluoride (1.2 mL, 1.2 mmol) was added slowly to a stirred solution
J O961494E