Organometallics
Article
solution (100 mL) at room temperature for 4 h. A clear orange solid
precipitated. The solid was filtered and dried in vacuum. The resulting
product was recrystallized from CH2Cl2/petroleum ether.
Scheme 3. Control Experiments for Mechanistic Studies
[RuCl(HL)(η6-p-cymene)]Cl (1). Orange solid (23 mg, 82% yield).
1H NMR (CDCl3, 400 MHz): δ = 14.13 (s br, 1H, NH),13.57 (s br,
1H, NH), 9.18 (d, 1H, Ru−NCH of pyrimidine, 3J = 4.0 Hz), 8.81
(s br, 1H, NCH−CH of pyrimidine), 8.24 (d, 1H, NCH of
pyrimidine, 3J = 3.2 Hz), 7.74 (s, 1H, O−CH of furane), 7.36 (s, 1H,
O−CHCH−CH of furane), 6.61 (d, 1H, O−CHCH of furane, 3J
= 0.2 Hz), 5.70 and 5.51 (AA′BB′ spin system, 2H, arom. CH of p-
cymene, 3J = 5.0 Hz), 5.59 and 5.46 (AA′BB′ spin system, 2H, arom.
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CH of p-cymene, J = 4.8 Hz), 2.96 (sept, 1H, CH(CH3)2), 2.03 (s,
3H, CH3 of p-cymene), 1.30 (d, 6H, CH(CH3)2, 3J = 7.0 Hz).
Elemental analysis calcd (%) for C20H22Cl2N4O2RuS: C, 43.32; H,
4.00; N, 10.10; S, 5.78. Found: C, 43.27; H, 3.98; N, 10.14; S, 5.75.
FT-IR (cm−1): 3433, 1572, 1438, 1256. UV−vis (CH2Cl2, λmax nm; ε
dm3 mol−1 cm−1): 438 (600), 296 (10 350), 238 (7350). The 13C
NMR spectrum could not be obtained due to poor solubility.
[RuCl2(L)(η6-mesitylene)] (2). Orange solid (20 mg, 76% yield). 1H
NMR (CDCl3, 300 MHz): δ = 14.48 (s, 1H, NH), 8.68 (d, 2H, N
CH of pyrimidine, 3J = 4.8 Hz), 7.57 (s, 1H, O−CH of furane), 7.31
Scheme 4. Intermolecular Competition Experiment between
EDG and EWG
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(d, 1H, O−CHCH−CH of furane, J = 3.3 Hz), 6.99 (t, 1H, N
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CH−CH of pyrimidine, J = 4.8 Hz), 6.59 (dd, 1H, O−CHCH of
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furane, J = 3.5 Hz and J = 1.6 Hz), 5.19 (s, 3H, arom. CH of
mesitylene), 2.27 (s, 9H, CH3 of mesitylene). 13C{1H} NMR (CDCl3,
126 MHz): δ = 180.94 (s, CS), 160.95 (s, Cq of pyrimidine),
157.40 (s, NCH of pyrimidine), 154.99 (s, HN−CO), 147.10 (s,
Cq of furane), 145.39 (s, O−CH of furane), 117.49 (s, O−CH
CH−CH of furane), 115.27 (s, NCH−CH of pyrimidine), 112.90
(s, O−CHCH of furane), 100.93 (s, Cq of mesitylene), 78.49 (s,
arom. CH of mesitylene), 19.77 (s, CH3 of mesitylene) ppm.
Elemental analysis calcd (%) for C19H19ClN4O2RuS: C, 45.28; H,
3.80; N, 11.12; S, 6.36. Found: C, 45.30; H, 3.83; N, 11.14; S, 6.33.
FT-IR (cm−1): 3441, 1571, 1421, 1266. UV−vis (CH2Cl2, λmax nm; ε
dm3 mol−1 cm−1): 407 (560), 295 (10 960), 247 (9400).
General Procedure for the Synthesis of Symmetrical Azines
(3a−3l). The mixture of alcohol (1 mmol), hydrazine hydrate (2
mmol), t-BuOK (1 mol %), catalyst (0.5 mol %), and 3 Å molecular
sieves (1 g) was stirred in toluene at 80 °C (oil bath). After 24 h, the
solvent was evaporated under reduced pressure. Then the resulting
residue was purified by silica gel column chromatography using
EtOAc/hexane to afford azines.
with a Vario EL III CHNS elemental analyzer. IR spectra were
recorded on a JASCO 400 plus spectrometer. Electronic spectra in
CH2Cl2 were recorded with a CARY 300 Bio UV-visible Varian
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spectrometer. H and 13C NMR spectra were recorded using Bruker
Avance-500, -400, or -300 NMR spectrometers in CDCl3 and
tetramethylsilane (TMS) as internal standard. Deuterated CDCl3 was
used as received. Chemical shifts were reported in units parts per
million (ppm) by assigning TMS resonance as 0.00 ppm with
reference to residual solvent signals (1H NMR: 7.26 ppm and 13C
NMR 77.00 ppm). Signal patterns are indicated as follows: s, singlet;
d, doublet; t, triplet; q, quartet; m, multiplet; br, broad.
Synthesis of HL1. A solution of 2-furoyl chloride (0.130 g, 1.0
mmol) was added dropwise to KSCN (0.097 g, 1.0 mmol) in
anhydrous acetone (40 mL) and refluxed for 1 h. The reaction
mixture was then allowed to cool to room temperature. A solution of
2-aminopyrimidine (0.095 g, 1.0 mmol) in acetone was added to the
reaction mixture and stirred at room temperature for 4 h. The
reaction mixture was then poured into 150 mL of 1 N dilute HCl acid
and was kept for overnight. The product gets precipitated, which was
filtered and dried in vaccuo. An analytically pure product was
obtained as yellow needles by recrystallization from acetone.
Competition Experiment between EDG and EWG. 4-Methox-
ybenzyl alcohol 2a (1 mmol), 4-chlorobenzyl alcohol 2c (1 mmol),
hydrazine hydrate (2 mmol), t-BuOK (1 mol %), catalyst 1 (0.5 mol
%), and 3 Å molecular sieves (1 g) were stirred in toluene at 80 °C
(oil bath) for 6 h. Furthermore, 3a and 3c were formed in 19 and 9%
yields, respectively.
N-(Pyrimidin-2-ylcarbamothioyl)furan-2-arboxamide (HL1). Yel-
low solid (0.198 g, 80% yield). 1H NMR (DMSO-d6, 400 MHz): δ =
14.07 (s, 1H, NH), 11.83 (s, 1H, NH), 8.81 (d, 2H, NCH of
pyrimidine, 3J = 5.2 Hz), 8.04 (s br, 1H, NCH−CH of pyrimidine),
(1E,2E)-1,2-Bis(4-methoxybenzylidene)hydrazine (3a).17 Yellow
solid (122 mg, 91% yield). 1H NMR (400 MHz, CDCl3): δ = 8.61 (s,
2H), 7.79 (m, 4H), 6.97 (m, 4H), 3.86 (s, 6H). 13C{1H} NMR (100
MHz, CDCl3): δ = 162.02, 161.14, 130.16, 127.01, 114.28, 55.43
ppm.
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7.50 (d, 1H, NCH of pyrimidine, J = 3.6 Hz), 7.32 (t, 1H, O−
CHCH−CH of furane), 6.77 (m, 1H, O−CHCH of furane).
13C{1H} NMR (DMSO-d6, 100 MHz): δ = 177.30 (s, CS), 158.39
(s, Cq of pyrimidine), 155.38 (s, HN−CO), 147.51 (s, Cq of
furane), 146.26 (s, O−CH of furane), 117.65 (s, O−CHCH−CH
of furane), 117.08 (s, NCH−CH of pyrimidine), 112.98 (s, O−
CHCH of furane) ppm. Elemental analysis calcd (%) for
C10H8N4O2S: C, 48.38; H, 3.25; N, 22.57; S, 12.92. Found: C,
48.31; H, 3.29; N, 22.53; S, 12.95. FT-IR (KBr, cm−1): 3434, 3213,
1728, 1565, 1412, 1284.
(1E,2E)-1,2-Bis(4-methylbenzylidene)hydrazine (3b).17 Yellow
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solid (100 mg, 85% yield). H NMR (400 MHz, CDCl3): δ = 8.64
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(s, 2H), 7.74 (d, 4H, J = 8.0 Hz), 7.24 (m, 4H), 2.41 (s, 6H).
13C{1H} NMR (100 MHz, CDCl3): δ = 161.90, 141.64, 131.49,
129.56, 128.54, 21.65 ppm.
(1E,2E)-1,2-Bis(4-chlorobenzylidene)hydrazine (3c).28 Yellow
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solid (113 mg, 82% yield). H NMR (400 MHz, CDCl3): δ = 8.60
Synthesis of Ruthenium Complexes 1 and 2. To a benzene
solution (20 mL) of N-(pyrimidin-2-ylcarbamothioyl)furan-2-
carboxamide(50 mg, 0.20 mmol) was added 0.10 mmol of the
appropriate ruthenium precursor (62 mg of [RuCl2(η6-p-cymene)]2
or 59 mg of [RuCl2(η6-mesitylene)]2). The reaction mixture was
stirred at room temperature for 4 h. A clear orange solid gets
precipitated. The solid was filtered and dried in vacuum. The resulting
complexes were recrystallized from CH2Cl2/petroleum ether.
Gram Scale Synthesis of Catalyst 1. N-(Pyrimidin-2-
ylcarbamothioyl)furan-2-carboxamide(0.50 g, 2.0 mmol) and
[RuCl2(η6-p-cymene)]2 (0.62 g, 1.0 mmol) were stirred in benzene
(s, 2H), 7.79 (d, 4H, 3J = 8.0 Hz,), 7.44 (d, 4H, 3J = 8.0 Hz). 13C{1H}
NMR (100 MHz, CDCl3): δ = 161.13, 137.37, 132.48, 129.78, 129.19
ppm.
(1E,2E)-1,2-Bis(4-nitrobenzylidene)hydrazine (3d).28 Yellow solid
(103 mg, 69% yield). 1H NMR (400 MHz, CDCl3): δ = 8.54 (s, 2H),
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7.65 (d, 4H, J = 8.4 Hz), 6.71 (d, 4H, J = 8.4 Hz). 13C{1H} NMR
(100 MHz, CDCl3): δ = 164.35, 157.97, 130.96, 127.03, 114.73 ppm.
(1E,2E)-1,2-Bis(2-methoxybenzylidene)hydrazine (3e).28 Yellow
solid (101 mg, 75% yield). 1H NMR (400 MHz, CDCl3): δ = 9.00 (s,
2H), 8.03 (d, 2H, 3J = 7.6 Hz), 7.35 (m, 2H), 6.95 (m, 2H), 6.86 (d,
E
Organometallics XXXX, XXX, XXX−XXX