1H), 7.15 (dt, J = 10.0, 2.0 Hz, 1H), 7.01 (dd, J = 8.0,
1.5 Hz, 1H), 6.83 (td, J = 8.0, 1.5 Hz, 1H); 13C NMR
(CDCl3, 125 MHz) δ 163.8 (d, JCF = 245.3 Hz, 1C),
143.2 (d, JCF = 10.4 Hz, 1C), 131.9, 131.7, 131.0 (d,
JCF = 9.4 Hz, 1C), 124.8, 119.7, 1115. (d, JCF = 21.5
Hz, 1C), 110.7 (d, JCF = 2.9 Hz, 1C), 105.3, 102.3 (d,
JCF = 26.8 Hz, 1C); 19F NMR (CDCl3, 376 MHz, 1H-
dc) δ -110.42 ppm; DART-HRMS found 324.90814
[M+H]+, calcd for C11H6Cl4FN2 324.92691.
DART-HRMS found 381.95616 [M]+, calcd for
C17H10Cl4N2 381.95981.
Representative procedure for synthesis of mono and
diacyl hydrazones.
Method A. N'-(Perchlorocyclopenta-2,4-dien-1-yli-
dene)benzohydrazide (4a). To
a
solution of
(perchloro-cyclopenta-2,4-dien-1-ylidene)hydrazine
(B, 116 mg, 0.5 mmol, 1.0 eq) in tetrahydrofuran (10
mL) was added benzoic anhydride (113 mg, 0.5
mmol, 1.0 eq) and triethylamine (0.07 mL, 0.5 mmol,
1.0 eq) dropwise in ice-bath. The reaction mixture
was stirred for 3 h at room temperature and then
concentrated in vacuo. The residue was diluted with
ethyl acetate (150 mL) and washed with water (2 X
50 mL) and brine (50 mL). The organic layer was
dried with MgSO4, filtered and concentrated in
vacuo. The residue was purified by flash column
chromatography over silica gel (hexane/ethyl acetate,
10:1, v/v) to afford the desired product 4a (239 mg,
71%) as brown solid: Rf = 0.45 (hexane/ethyl acetate,
1-(3-Methoxyphenyl)-2-(perchlorocyclopenta-2,4-
dien-1-ylidene)hydrazine (3i). Red brown solid
(50% yield): Rf = 0.4 (hexane/ethyl acetate, 10:1,
1
v/v); mp 123-125 °C; H NMR (CDCl3, 500 MHz) δ
10.66 (s, 1H), 7.27 (t, J = 8.0 Hz, 1H), 6.96 (s, 1H),
6.84 (dd, J = 8.0, 1.0 Hz, 1H), 6.69 (dd, J = 8.0, 1.5
Hz, 1H), 3.85 (s, 3H); 13C NMR (CDCl3, 125 MHz) δ
161.0, 142.7, 131.0, 130.9, 130.5, 124.0, 119.4, 110.7,
107.7, 105.0, 100.6, 55.4 ppm; DART-HRMS found
336.92801 [M+H]+, calcd for C12H8Cl4N2O
336.94690.
1
5:1, v/v); mp 170-172 °C; H NMR (DMSO-d6, 500
1-(2-Fluorophenyl)-2-(perchlorocyclopenta-2,4-
dien-1-ylidene)hydrazine (3j). Red brown solid
(52% yield): Rf = 0.6 (hexane/ethyl acetate, 20:1,
v/v); mp 120-122 °C; 1H NMR (DMSO-d6, 500 MHz)
δ 11.16 (s, 1H), 7.65 (t, J = 8.0 Hz, 1H), 7.36 (dd, J =
10.0 Hz, 1H), 7.29 (t, J = 7.5 Hz, 1H), 7.20 (dd, J =
12.5, 6.0 Hz, 1H), 3.32 (s, 3H); 13C NMR (CDCl3,
125 MHz) δ 151.1 (d, JCF = 242.4 Hz, 1C), 132.7,
131.8, 130.1, (d, JCF = 8.4 Hz, 1C), 125.3 (d, JCF = 3.5
Hz, 1C), 124.8, 124.6 (d, JCF = 7.3 Hz, 1C), 119.5,
115.6, 115.5 (d, JCF = 17.4 Hz, 1C), 105.6; 19F NMR
MHz) δ 11.98 (s, 1H), 7.93 (d, J = 7.5 Hz, 2H), 7.69
(t, J = 7.5 Hz, 1H), 7.59 (t, J = 7.5 Hz, 2H); 13C NMR
(DMSO- d6, 125 MHz) δ 164.8, 140.8, 135.0, 133.7,
132.1, 129.5, 129.3, 128.7, 120.8, 109.7 ppm; DART-
HRMS found 334.91239 [M+H]+, calcd for
C12H7Cl4N2O 334.93125.
N-Benzoyl-N'-(perchlorocyclopenta-2,4-dien-1-
ylidene)benzohydrazide (4b). Dark brown solid
(52% yield): Rf = 0.65 (hexane/ethyl acetate, 5:1,
1
1
(CDCl3, 376 MHz, H-dc) δ -135.16 ppm; DART-
v/v); mp 123-124 °C; H NMR (CDCl3, 500 MHz) δ
HRMS found 324.90775 [M+H]+, calcd for
C11H6Cl4FN2 324.92691.
7.15 (dd, J = 8.5, 1.0 Hz, 2H), 8.02 (dd, J = 8.5, 1.0
Hz, 2H), 7.68 (tt, J = 7.5, 1.0 Hz, 1H), 7.56 (t, J = 7.5
Hz, 1H), 7.53 (t, J = 7.5 Hz, 2H), 7.48 (t, J = 7.5 Hz,
2H); 13C NMR (CDCl3, 125 MHz) δ 162.1, 151.0,
149.4, 137.7, 134.4, 132.6, 132.5, 130.6, 130.0, 128.9,
128.8, 128.1, 127.6, 120.2, 112.4 ppm; DART-HRMS
found 438.93702 [M+H]+, calcd for C19H11Cl4N2O2
438.95747.
1-(4-Fluorophenyl)-2-(perchlorocyclopenta-2,4-
dien-1-ylidene)hydrazine (3k). Brown solid (48%
yield): Rf = 0.6 (hexane/ethyl acetate, 5:1, v/v); mp
1
147-149 °C; H NMR (DMSO-d6, 500 MHz) δ 11.64
(s, 1H), 7.59-7.56 (m, 2H), 7.30-7.26 (m, 2H); 13C
NMR (CDCl3, 125 MHz) δ 160.0 (d, JCF = 243.3 Hz,
1C), 137.8, 131.0, 130.9, 124.1, 119.4, 116.5 (d, JCF
=
N'-(Perchlorocyclopenta-2,4-dien-1-ylidene)aceto-
hydrazide (4c). Brown solid (89% yield): Rf = 0.7
23.1 Hz, 1C), 116.4 (d, JCF = 7.9 Hz, 1C), 104.9; 19F
NMR (CDCl3, 376 MHz, 1H-dc) δ -117.44 ppm;
DART-HRMS found 324.90593 [M+H]+, calcd for
C11H6Cl4FN2 324.92691.
1
(hexane/ethyl acetate, 5:1, v/v); mp 145-147 °C; H
NMR (CDCl3, 500 MHz) δ 10.62 (s, 1H), 2.42 (s,
3H); 13C NMR (CDCl3, 125 MHz) δ 173.6, 136.3,
135.1, 129.1, 120.9, 107.5, 19.6 ppm; DART-HRMS
found 272.89722 [M+H]+, calcd for C7H4Cl4N2O
272.91560.
2-(Perchlorocyclopenta-2,4-dien-1-ylidene)-1,1-
diphe-nylhydrazine (3l). Dark red solid (78% yield):
Rf = 0.6 (hexane/ethyl acetate, 10:1, v/v); mp 128-130
°C; 1H NMR (DMSO-d6, 500 MHz) δ 7.48 (t, J = 7.5
Hz, 4H), 7.37 (t, J = 7.0 Hz, 2H), 7.34 (d, J = 7.5 Hz,
4H); 13C NMR (DMSO-d6, 125 MHz) δ 146.5, 132.2,
131.7, 130.4, 128.3, 123.6, 123.0, 121.7, 106.4 ppm;
N'-(Perchlorocyclopenta-2,4-dien-1-ylidene)pivalo-
hydrazide (4d). Red brown solid (71% yield): Rf =
0.5 (hexane/ethyl acetate, 5:1, v/v); mp 156-158 °C;
1H NMR (DMSO-d6, 500 MHz) δ 11.17 (s, 1H), 1.24
11