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2002 Marcel Dekker, Inc. All rights reserved. This material may not be used or reproduced in any form without the express written permission of Marcel Dekker, Inc.
NITRILES FROM O-ARYLALDOXIMES CATALYZED BY ZrCl4
3875
without further purification. Compound 6a and N-phenoxy- and N-( p-
[
cyanophenoxy)-amines were prepared by the published procedures.
3–5]
Synthesis of p-Methoxybenzaldehyde
O-( p-Cyanophenyl)oxime (1e), Typical Procedure
To a stirred solution of acetonitrile (8 mL) and H O (4 mL) containing
2
anisaldehyde (300 mg, 2.20 mmol) was added N-( p-cyanophenoxy)amine
(
(
(
355 mg, 2.64 mmol). After stirring the reaction mixture for 10 min, H O
2
10 mL) was added and the aqueous layer was extracted with EtOAc
20 mL ꢂ 2). The combined organic layers were washed with brine (20 mL),
dried (Na SO ), and concentrated. The residue was recrystallized from ben-
2
4
zene/hexane to afford the pure 1e (234 mg) as white crystals. The filtrate was
concentrated and the residue was chromatographed on a column of silica gel
(
30 g) using benzene/hexane (5 : 1) as eluent to afford 1e (289 mg, total yield,
94%). Physical and analytical data are presented in Tables 3 and 4.
Synthesis of p-Methoxybenzonitrile (3e), Typical Procedure
To a stirred solution of nitromethane (4 mL) containing 1e (100 mg,
.396 mmol) was added ZrCl (185 mg, 0.792mmol). After refluxing the reac-
0
tion mixture for 2min, H O (10 mL) was added with cooling and the aqueous
4
2
layer was extracted with EtOAc (25 mL ꢂ 2). The combined organic layers
were washed with brine (25 mL), dried (Na SO ), and concentrated. The
2
4
residue was chromatographed on a column of silica gel (10 g). Elution with
benzene/EtOAc (20 : 1) afforded initially 3e (49 mg, 93%) as white crystals;
ꢁ
[6]
m.p. 56–58 C (lit. m.p. 58–59 C). Further elution with the same solvent
ꢁ
ꢁ
[7]
mixture afforded p-cyanophenol (43 mg, 91%); m.p. 110–112 C (lit. m.p.
ꢁ
1
12.0–112.4 C). Physical data for 3 are listed in Table 5.
Synthesis of 4-Oxo-4H-1-benzopyran-3-carbonitrile (5)
A mixture of 6b (200 mg, 0.689 mmol), ZrCl (321 mg, 1.38 mmol) and
4
nitromethane (50 mL) was refluxed for 5 h. After evaporation of the solvent
in vacuo, H O (50 mL) was added to the residue and the aqueous layer was
2
extracted with EtOAc (50 mL ꢂ 2). The combined organic layers were
washed with brine (50 mL), dried (Na SO ), and concentrated. The residue
2
4
was chromatographed on a column of silica gel (35 g). Elution with
benzene/EtOAc (30 : 1) first afforded 5 (98 mg, 83%) as white crystals;