470
S. Baaziz et al. / Tetrahedron 72 (2016) 464e471
NMR (CDCl3, 75 MHz)
d
(ppm) 21.4, 103.0, 118.9, 129.2, 129.6, 130.8,
column chromatography using CH2Cl2/PE (4/1) as eluent to afford
133.7, 134.0, 155.1, 159.0, 174.3, 180.0, 184.8; 11B NMR (CDCl3,
8c (608 mg) in 75% yield as a pale yellow powder; mp 199 ꢀC; 1H
96 MHz)
UVevis
d
(ppm) 0.14; 19F NMR (CDCl3, 282 MHz)
d
(ppm) ꢁ141.9;
NMR (CDCl3, 300 MHz)
5.76 (s,1H,¼CH), 7.43e7.52 (m, 3H, Ar), 7.66 (d, 2H, J¼8 Hz, Ar); 8.29
(s, 1H, N]CH); 13C NMR (CDCl3, 75 MHz)
(ppm) 17.1, 19.9, 96.0,
d (ppm) 2.17 (s, 3H, CH3), 3.00 (s, 3H, CH3),
l
(ε)¼339 nm (11,500), 406 nm (40,000); IR (cmꢁ1
)
n
¼2925,
1732, 1631, 1618, 1539, 1501; HRMS calcd for [MþH]þ
d
(C15H12O411BF2): 305.0791, found: 305.0796.
107.0, 128.3, 129.0, 131.8, 132.7, 154.3, 163.1, 163.5, 172.9, 184.6;
UVevis
l
(ε)¼365 nm (39,000), 379 nm (35,000); IR (cmꢁ1
)
General procedure for the synthesis of 6a, b. To difluoroborane
complex 5a (100 mg, 0.24 mmol) or 5b (20 mg, 0.042 mmol) was
added sodium carbonate (1.0 g, 0.94 mmol) dissolved in a mixture
of water (5 mL) and EtOH (5 mL). The medium was refluxed for 2 h.
The reaction mixture was cooled and treated with a solution of
hydrochloric acid till pH reached 6.5e7. The precipitate that formed
was filtered, extracted with CH2Cl2, washed with water and dried
over magnesium sulfate. The product was purified by column
chromatography using CH2Cl2/PE (4/1) as eluent.
n¼2958, 2923, 1702, 1656, 1608, 1574, 1553; HRMS calcd for
[MþNa]þ C15H14N2O3Na: 293.0902, found: 293.0904; Anal. Calcd
for C15H14N2O3: C, 66.66, H, 5.22, N, 10.36; found C, 66.59, H, 5.10, N,
10.31%.
General procedure for the synthesis of 9aec. An excess of Et2O$BF3
(0.63 mL, 5 mmol) was added to a solution of 8a (189 mg, 0.5 mmol)
or 8b (220 mg, 0.5 mmol) 8c (135 mg, 0.5 mmol) containing dry
NEt3 (0.21 mL,1.5 mmol) in 15 mL of dry and degassed CH2Cl2 under
inert atmosphere. The reaction mixture was stirred at room tem-
perature for 12 h. The organic phase was washed with water and
dried over MgSO4 and subjected to column chromatography using
CH2Cl2 as eluent.
6a (65 mg) was obtained as a deep purple powder in 75% yield;
mp 159e160 ꢀC; 1H NMR (CDCl3, 300 MHz)
d (ppm) 2.25 (s, 3H,
CH3), 4.20 (s, 5H, Cp), 4.57 (s, 2H, Cp), 4.68 (s, 2H, Cp), 5.92 (s,
1H,¼CH), 7.86 (d, 1H,¼CH, J¼16 Hz), 7.99 (d, 1H,¼CH, J¼16 Hz); 13
C
NMR (CDCl3, 75 MHz)
d
(ppm) 20.6, 69.9, 70.1, 72.4, 79.0, 98.9,
9a (164 mg) was obtained as a red solid in 77% yield; mp 206 ꢀC;
102.9, 119.3, 150.0, 161.4, 167.8, 183.7, 190.9; UVevis
l
(ε)¼365 nm
1H NMR (CDCl3, 300 MHz)
d (ppm) 2.31 (s, 3H, CH3), 2.81 (s, 3H,
(32,500), 550 nm (7500); IR (cmꢁ1
)
n
¼1716, 1652, 1609, 1504;
CH3), 4.32 (s, 5H, Cp), 4.58 (t, 2H, J¼2 Hz, Cp), 4.76 (s, 2H, J¼2 Hz,
HRMS calcd for Mþ (C19H16O456Fe): 364.0398, found: 364.0410.
Cp), 6.07 (s, 1H,¼CH), 8.63 (s, 1H,¼CH); 13C NMR (CDCl3, 75 MHz)
6b (11 mg) was obtained as a deep blue powder in 64% yield;
d (ppm) 17.9, 20.6, 69.4, 70.0, 72.5, 77.2, 96.7, 102.4, 160.5, 164.8,
mp>250 ꢀC; 1H NMR (CDCl3, 300 MHz)
d
(ppm) 1.95 (s, 3H, CH3),
167.6, 168.8, 172.3; 11B NMR (CDCl3, 96 MHz)
NMR (CDCl3, 282 MHz)
d
(ppm) ꢁ19.39; 19F
1.96 (s, 3H, CH3), 2.27 (s, 6H, CH3), 5.93 (s,1H,¼CH), 7.46 (d,1H,¼CH,
d
(ppm) ꢁ136.6; UVevis
l
(ε)¼289 nm
J¼15 Hz), 7.73 (d, 1H,¼CH, J¼15 Hz), 17.89 (s, 1H, OH); 13C NMR
(45,000), 353 nm (111,000), 500 nm (19,000); IR (cmꢁ1
)
n
¼1712,
(CDCl3, 75 MHz)
d
(ppm) 13.8, 14.8, 20.8, 99.6, 102.5, 113.1, 122.7,
1650, 1609, 1562, 1506; HRMS calcd for Mþ (C19H17N2O311BF256Fe):
426.0650, found: 426.0660.
123.4, 124.0, 128.9, 129.6, 133.1, 144.8, 161.1, 168.7, 183.1, 192.0;
UVevis
n
l
(ε)¼368 nm (32,600), 600 nm (8200); IR (KBr, cmꢁ1
)
9b (56 mg) was obtained as a red solid in 23% yield; mp>260 ꢀC;
¼2921, 1716, 1638, 1618, 1509; HRMS calcd for Mþ (C18H16O4S4):
1H NMR (CDCl3, 300 MHz)
d (ppm) 1.96 (s, 6H, CH3), 2.33 (s, 3H,
423.9926, found: 423.9930.
CH3), 2.92 (s, 3H, CH3), 6.06 (s, 1H,¼CH), 8.65 (s, 1H,¼CH); 11B NMR
(CDCl3, 96 MHz)
d
(ppm) ꢁ0.14; 19F NMR (CDCl3, 282 MHz)
d (ppm)
General procedure for the synthesis of 8a, b. To a solution of DHA-
hydrazone 7 (182 mg, 1 mmol) in THF (15 mL) was added ferro-
cenecarboxaldehyde (214 mg, 1 mmol) or Me3TTFcarboxaldehyde
(274 mg, 1 mmol) and 2 mL of HCl 2 M. The reaction mixture was
refluxed 2 h. The solvent was removed under vacuum, the solid
was extracted with CH2Cl2, washed with water and dried over
MgSO4.
ꢁ136.4; UVevis
l
(ε)¼369 nm (34,000), 558 nm (6700); HRMS
calcd for Mþ (C18H17N2O311BF2): 486.01832, found: 486.0184.
9c (95 mg) was obtained as a yellow solid in 60% yield; mp
202 ꢀC; 1H NMR (CDCl3, 300 MHz)
d (ppm) 2.34 (s, 3H, CH3), 2.96 (s,
3H, CH3), 6.08 (s, 1H,¼CH), 7.45e7.57 (m, 3H, Ar), 7.86 (d, 2H,
J¼6 Hz, Ar); 8.78 (s, 1H,¼CH); 13C NMR (CDCl3, 75 MHz)
d (ppm)
18.2, 20.7, 96.9, 102.4, 129.1, 129.2, 132.8, 132.9, 160.4, 162.4, 169.7,
8 was purified by column chromatography using CH2Cl2 as el-
170.4, 173.0; 11B NMR (CDCl3, 96 MHz)
d
(ppm) ꢁ0.07; 19F NMR
uent to afford a red solid in 74% yield (280 mg); mp 154 ꢀC; 1H NMR
(CDCl3, 282 MHz)
d
ꢁ136.6; UVevis
l
(ε)¼358 nm (26,500); IR
(CDCl3, 300 MHz)
d
(ppm) 2.16 (s, 3H, CH3), 2.89 (s, 3H, CH3), 4.23 (s,
(cmꢁ1
)
n
¼1731, 1637, 1510, 1449; HRMS calcd for [MþNa]þ
5H, Cp), 4.53 (s, 2H, Cp), 4.69 (s, 2H, Cp), 5.75 (s, 1H,¼CH), 8.20 (s,
C15H13N2O311BF2Na: 341.0885, found: 341.0884.
1H,¼CH), 16.71 (s, 1H, OH); 13C NMR (CDCl3, 75 MHz)
d (ppm) 17.2,
20.0, 68.8, 69.6, 71.8, 76.5, 95.6, 107.2, 156.4, 163.2, 163.5, 170.9,
4.3. Crystallography
184.5; UVevis
l
(ε)¼248 nm (86,000), 361 nm (133,000), 376 nm
(122,000), 483 nm (22,000); IR (cmꢁ1
)
n
¼1707, 1659, 1600, 1562;
Single-crystal diffraction data were collected on APEX II Bruker
HRMS calcd for Mþ (C19H18N2O356Fe): 378.0667, found: 378.0672.
Anal. Calcd for C19H18FeN2O3: C, 60.34, H, 4.80, N, 7.41, found C,
60.04, H, 4.73, N, 7.10%.
AXS diffractometer, Mo K
a
radiation (
l
¼0.71073 A), for compounds
ꢁ
ꢀ
ꢀ
5a, 5b, 7, 8a and 9a (Centre de Diffractometrie X, Universite de
Rennes, France). The structures were solved by direct methods
using the SIR97 program,19 and then refined with full-matrix least-
square methods based on F2 (SHELX-97)20 with the aid of the
WINGX program.21 All non-hydrogen atoms were refined with
anisotropic atomic displacement parameters. H atoms were finally
included in their calculated positions.
8b was purified by column chromatography using CH2Cl2/MeOH
(9.8/0.2) as eluent to afford a deep purple powder in 53% yield
(232 mg); mp 274 ꢀC; 1H NMR (CDCl3, 300 MHz)
d
(ppm) 1.96 (s, 6H,
CH3), 2.17 (s, 3H, CH3), 2.26 (s, 3H, CH3), 2.88 (s, 3H, CH3), 5.74 (s,1H,
CH), 8.09 (s, 1H, CH]N); 13C NMR (CDCl3, 75 MHz)
(ppm) 12.7,
12.7, 13.4, 16.0, 18.9, 95.1, 105.8, 112.1, 121.7, 122.1, 142.6, 142.8, 142.9,
162.0, 162.7, 171.6, 183.6; UVevis (ε) 369 nm (34,400), 383 nm
d
Crystal data for 5a: (C19H15BF2FeO4); M¼411.97. T¼294 (2) K;
ꢁ
l
)
monoclinic P 21/c, a¼11.323 (5), b¼10.313 (7), c¼15.246 (9) A,
(36,300), 525 nm (6600); IR (cmꢁ1
n
¼1616, 1590; HRMS calcd for
b
m
¼103.71 (3)
,
V¼1729.6 (17) A , Z¼4, d¼1.582
g ,
cmꢁ3
3
ꢀ
ꢁ
Mþ (C18H18N2O3S4) 438.0200, found 438.0194.
¼0.915 mmꢁ1. A final refinement on F2 with 3903 unique in-
tensities and 245 parameters converged at
u
R(F2)¼0.1034 (R(F)¼
Synthesis of 8c. To a solution of DHA-hydrazone 7 (546 mg,
3 mmol) in absolute EtOH (15 mL) was added benzaldehyde
(0.3 mL, 3 mmol). The reaction mixture was refluxed for 3 h. The
solvent was removed under vacuum and the solid was subjected to
0.0429) for 2554 observed reflections with I>2s(I).
Crystal data for 5b: (C18H15BF2O4S4); M¼472.35. T¼150 (2) K;
monoclinic P 21/c, a¼14.6844 (17), b¼12.3494 (15), c¼11.3986
3
ꢁ
ꢁ3
,
ꢀ
ꢁ
(10) A,
b
¼102.523 (4) , V¼2017.9 (4) A , Z¼4, d¼1.555 g cm