Transit Met Chem
Synthesis of N1,N3-diphenyl-1,3-benzenedicarboxamide
(4c)
Stoichiometric ratio of 2-bromoisophthalic acid and
benzene (64 mL) was placed in a 100-mL flask immersed
in an ice-water bath. SOCl2 (9 mL, 100 mmol) was added
dropwise, and the mixture was refluxed for 5 h and evap-
orated under reduced pressure to remove excess SOCl2.
The solid product was dissolved in benzene, and then the
resultant suspension was filtered and concentrated to give a
pale yellow solid in 75% yield. 1H NMR (500 MHz,
CDCl3): 8.01 (d, 2H), 7.61 (t, 1H); 13C NMR (75 MHz,
CDCl3) d 166.1, 139.1, 134.5, 127.9, 117.3.
Compounds 4c were prepared following the procedures
reported previously [33]. To a solution of benzenamine
(1.02 g, 11.0 mmol) in CH2Cl2 (20 mL) was added drop-
wise
a solution of 2-bromo-1, 3-benzenedicarbonyl
dichloride 2 (1.41 g, 5.0 mmol) in CH2Cl2 (20 mL) at
0 °C. After it was warmed to room temperature and stirred
overnight, the mixture was washed with 10% aqueous
NaOH (2 9 20 mL), water (2 9 20 mL), and 10% HCl
(2 9 20 mL). The organic layer was washed with water,
dried with anhydrous Na2SO4, and concentrated to afford a
white solid. Yield: 1.63 g (83%). 1H NMR (500 MHz,
DMSO-d6, 25 °C, TMS): 10.54 (s, 2H, amide NH), 7.72 (d,
J = 7.6 Hz, 2H, aromatic H), 7.64–7.56 (m, 4H, aromatic
H), 7.28–7.25 (m, 4H, aromatic H), 7.10 (t, J = 7.6 Hz,
3H, aromatic H); 13C NMR (75 MHz, DMSO-d6, 25 °C,
TMS):167.6, 140.6, 139.4, 128.5, 128.2, 127.6, 127.0,
125.7, 120.5. Anal. Calc. for C20H15O2N2Br: C, 60.78, H,
3.83, N, 20.22; Found: C, 60.80, H, 3.85, N, 20.39.
Synthesis of N1,N3-bis(1H-pyrazol-3-yl)-1,3-
benzenedicarboxamide (4a)
To a solution of 2-bromo-1,3-benzenedicarbonyl dichloride
2 (1.41 g, 5.0 mmol) in dried acetonitrile (10 mL) was
slowly added a solution of 1H-pyrazol-3-amine (0.91 g,
11.0 mmol) in acetonitrile (10 mL). After it was refluxed
overnight under nitrogen atmosphere, the precipitate so
obtained was filtered off and dried in vacuum. The solid
was dissolved in methanol, excess triethylamine was
added, the mixture was stirred at room temperature over-
night, and white solid compound was obtained, filtered off,
washed with cold water, and dried. Yield: 1.41 g (75%). 1H
NMR (500 MHz, DMSO-d6, 25 °C, TMS): 12.29 (s, 2H,
pzNH), 10.66 (s, 2H, amide NH), 8.11 (m, 2H, aromatic
H), 7.69–7.65 (d, J = 5.6 Hz, 2H, pz H), 7.61 (m, 1H,
aromatic H), 6.68 (d, J = 6.6 Hz, 2H, pz H); 13C NMR
(75 MHz, DMSO-d6, 25 °C, TMS):165.1, 145.3, 139.1,
134.4, 132.6, 131.6, 128.8, 95.6. Anal. Calc. for C14H11-
O2N6Br: C, 44.82, H, 2.96, N, 22.40; Found: C, 44.80, H,
2.95, N, 22.39.
Typical procedure for (NCN)PdBr pincer complexes
The synthetic procedure for (NCN)PdBr pincer complexes
is illustrated in Scheme 2. A Schlenk flask equipped with a
magnetic bar was loaded with 4a–4c (1 equiv), anhydrous
toluene (30 mL), Pd2(dba)3 (1.1 equiv) and sealed with a
screw cap. The mixture was stirred at 40 °C overnight. The
reaction mixture was filtered through silica eluting with
toluene and washed with ethyl acetate to give a yellow
solution, and the solvent was removed under reduced
pressure to give 5a–5c.
Synthesis of N1,N3-bis(5-methyl-1H-pyrazol-3-yl)-1,3-
benzenedicarboxamide (4b)
Synthesis of 5a
A Schlenk flask equipped with a magnetic bar was loaded
with 4a (56.3 mg, 0.15 mmol), anhydrous toluene
(30 mL), Pd2(dba)3 (72.7 mg, 0.16 mmol) and sealed with
a screw cap. The mixture was stirred at 40 °C overnight.
The reaction mixture was filtered through silica eluting
with toluene and washed with ethyl acetate to give a yellow
solution, and the solvent was removed under reduced
pressure to give 5a as a yellow solid. Yield: 47.0 mg
(65%). 1H NMR (500 MHz, DMSO-d6, 25 °C. TMS):
12.48 (s, 2H, pzNH), 10.81 (s, 2H, amide NH), 8.07 (m,
2H, aromatic H), 7.71–7.75 (d, J = 5.6 Hz, 2H, pz H), 7.61
(m, 1H, aromatic H), 6.83 (d, J = 4.3 Hz, 2H, pz H); 13C
NMR (75 MHz, DMSO-d6, 25 °C, TMS):170.4, 159.9,
145.6, 136.6, 134.5, 133.5, 131.0, 96.5. Anal. Calc. for
C14H11O2N6PdBr: C, 34.91, H, 2.30, N, 17.45; Found: C,
34.93, H, 2.30, N, 17.45. HRMS (positive ESI) Calc. for
C14H12O2N6PdBr (MH?): 482.5143; found: 482.5264.
To a solution of 2-bromo-1,3-benzenedicarbonyl dichloride
2 (1.41 g, 5.0 mmol) in dried acetonitrile (10 mL) was
slowly added a solution of 5- methyl-1H-pyrazol-3-amine
(1.07 g, 11.0 mmol) in acetonitrile (10 mL). After it was
refluxed overnight under nitrogen atmosphere, the precip-
itate so obtained was filtered off and dried in vacuum. The
solid was dissolved in methanol, excess triethylamine was
added, the mixture was stirred at room temperature over-
night, and white solid compound was obtained, filtered off,
washed with cold water, and dried. Yield: 1.45 g (72%). 1H
NMR (500 MHz, DMSO-d6, 25 °C, TMS): 12.43 (s, 2H,
pzNH), 10.68 (s, 2H, amide NH), 8.09 (m, 2H, aromatic
H), 7.59 (m, 1H, aromatic H), 6.47 (d, 2H, J = 5.6 Hz, pz
H), 2.78 (s, 6H, methyl H); 13C NMR (75 MHz, DMSO-d6,
25 °C, TMS):165.5, 149.6, 139.4, 135.1, 132.2, 129.4,
127.6, 97.1, 13.6. Anal. Calc. for C16H15O2N6Br: C, 47.66,
H, 3.75, N, 20.84; Found: C, 47.80, H, 3.69, N, 20.89.
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