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anhydrous MgSO4, filtered and concentrated to give 3,4-diamino-
phenyl acetate (50 mg, 61%) that was used directly for the next
step.
Synthesis
[Ru(bipy)2-dppz-7-amino][PF6]2 (1)
1 was synthesized as previously reported.[58,59] Experimental data fit
with the literature. Purity of 1 was assessed by elemental analysis.
Elemental analysis calcd for C38H33F12N9O3P2Ru (%): C 43.27, H 3.15,
N 11.95; found: C 43.44, H 3.11, N 11.95.
A stirred solution of 3,4-diaminophenyl acetate (40 mg, 0.24 mmol)
and [Ru(bipy)2phendione](PF6)2 (146 mg, 0.16 mmol) in 16 mL of
1:3 CH3CN/EtOH (v/v) was heated at 758C under N2 atmosphere.
After 2.5 h, the mixture was concentrated using a rotary evaporator
and cooled to room temperature. Addition of a sat. NH4PF6 (10 mL)
solution resulted in the formation of an orange precipitate. The
precipitate was filtered, washed with distilled water, ice cold etha-
nol and finally with diethyl ether to give 3 as a red-orange powder
(yield: 109 mg, 65%). 1H NMR (500 MHz, [D6]DMSO): d=2.45 (s,
3H), 7.40 (t, 2H), 7.61 (t, 2H), 7.76 (d, 2H), 7.84 (d, 2H), 8.02–8.07
(m, 3H), 8.15 (t, 2H), 8.22–8.26 (m, 4H), 8.30 (d, 1H), 8.57 (d, 1H),
8.89 (dd, 4H), 9.62 (d, 1H), 9.64 ppm (d, 1H); 13C NMR (126 MHz,
[D6]DMSO): d=21.6, 120.3, 124.8, 124.9, 128.1, 128.3, 129.2, 130.4,
130.5, 131.1, 133.6, 133.7, 138.4, 138.5, 140.3, 140.5, 140.9, 142.7,
150.7, 150.8, 151.8, 152.3, 153.3, 153.8, 154.0, 156.9, 157.2,
169.5 ppm; ESI-MS (pos. detection mode): m/z (%): 376.9 (100)
[Mꢀ2PF6]2+. Elemental analysis calcd for C40H28F12N8O2P2Ru: C
46.03, H 2.70, N 10.74; found: C 45.90, H 2.68, N 10.79.
[Ru(bipy)2-dppz-7-methoxy][PF6]2 (2)[60]
The complex was prepared by adapting a literature reported pro-
cedure (yield: 282 mg, 72%), since the hexafluorophosphate salt of
[Ru(bipy)2phendione]2+ was used as precursor and 2 was isolated
as PF6 salt.[60] The spectroscopic data match well with those re-
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ported for the complex with a ClO4 counter anion. The purity of 2
was checked by elemental analysis. Elemental analysis calcd for
C39H28F12N8OP2Ru: C 46.12, H 2.78, N 11.03; found: C 46.03, H 2.75,
N 10.96.
4-Hydroxy-phenylenediamine dicarbamate
THF (10 mL) was added to a mixture of 4-hydroxy-phenylenedia-
mine (100 mg, 0.81 mmol) and di-tert-butyl dicarbonate (385 mg,
1.77 mmol). The mixture was stirred for 24 h at room temperature
under N2 atmosphere. THF was then evaporated and the residue
was dissolved in EtOAc (50 mL). The organic phase was then
washed with 0.5m HCl (until the aqueous layer became colorless),
distilled water (1ꢂ50 mL) and brine (1ꢂ50 mL). The organic phase
was then dried over anhydrous MgSO4, filtered and concentrated.
Flash column chromatography (silica gel, hexane/EtOAc 3:1!2:1)
gave the product as a white solid (yield: 112 mg, 43%). 1H NMR
(400 MHz, [D6]acetone): d=1.49 (s, 9H), 1.51 (s, 9H), 6.58 (m, 1H),
7.15 (d, 1H), 7.29 (s, 1H), 7.70 (s, br, 1H), 7.77 (s, br, 1H), 8.26 ppm
(s, 1H); 13C NMR (100.6 MHz, [D6]acetone): d= 27.5, 27.6, 79.1, 79.3,
109.1, 110.5, 121.1, 126.5, 133.6, 153.0, 154.3, 155.1 ppm; ESI-MS
(pos. detection mode): m/z (%): 347.1 (100) [M+Na]+.
[Ru(bipy)2-dppz-7-hydroxy][PF6]2 (4)
To a stirred solution of 3 (50 mg, 0.048 mmol) in MeOH (6 mL), 1m
aq. NaOH (4 mL) was added. After being stirred at room tempera-
ture for 1.5 h, the reaction mixture was concentrated and acidified
with 1m HCl until pH of about 2. The color of the solution
changed from deep red to light orange upon acidification. Solid
NH4PF6 was then added until the precipitation was complete. The
orange precipitate was then filtered, washed with distilled water
(10 mL), ice-cold ethanol (10 mL) and finally with diethyl ether
(15 mL) to give 4 as an orange powder (yield: 45 mg, 94%).
1H NMR (500 MHz, [D6]DMSO): d=7.38 (t, 2H), 7.59–7.62 (m, 3H),
7.75–7.78 (m, 3H), 7.84 (d, 2H), 7.98–8.01 (m, 2H), 8.12–8.24 (m,
6H), 8.37 (d, 1H), 8.87 (dd, 4H), 9.55 (d, 1H), 9.62 (d, 1H),
11.34 ppm (s, br, 1H); 13C NMR (126 MHz, [D6]DMSO): d=108.5,
124.8, 124.9, 127.2, 127.9, 128, 128.2, 128.3, 130.5, 130.8, 131.4,
133.1, 133.5, 137.3, 138.3, 138.4, 140.3, 144.6, 149.7, 150.8, 151.8,
152.3, 153.1, 153.6, 156.9, 157.2, 161.6 ppm; ESI-MS (pos. detection
mode): m/z (%): 356 (100) [Mꢀ2PF6]2+. Elemental analysis calcd for
C38H26F12N8OP2Ru·H2O: C 44.76, H 2.77, N 10.99; found: C 44.87, H
2.79, N 10.93.
4-Acetoxy-phenylenediamine dicarbamate (7)
NEt3 (311 mg, 3.08 mmol) and acetyl chloride (0.2 mL, 3.08 mmol)
were added to a stirred solution of 4-hydroxy-phenylenediamine
dicarbamate (200 mg, 0.62 mmol) in CH2Cl2 (25 mL). After being
stirred at room temperature for 1.5 h, the reaction mixture was di-
luted with CH2Cl2 (100 mL). The organic phase was washed with
sat. NaHCO3 (1ꢂ100 mL), distilled water (1ꢂ100 mL) and brine (1ꢂ
50 mL). The organic phase was then dried over anhydrous MgSO4,
filtered and concentrated. Flash column chromatography (silica gel,
hexane/EtOAc 3:1!2:1) gave 7 as a white sticky solid (yield:
3,4-Diaminobenzoic acid ethyl ester
Concentrated sulfuric acid (12 mL) was added dropwise to a solu-
tion of 3,4-diaminobenzoic acid (1.30 g, 8.54 mmol) in EtOH
(100 mL). The mixture was then refluxed for 6 h. The solution was
neutralized by the addition of sat. NaHCO3 (300 mL). The neutral
aqueous solution was extracted with EtOAc (200 mL). The reunited
organic phases were dried over anhydrous MgSO4, filtered and the
solvent was evaporated to afford the product as a brown powder
1
205 mg, 91%). H NMR (500 MHz, CDCl3): d=1.40 (s, 18H), 2.15 (s,
3H), 6.37 (s, br, 1H), 6.72–6.78 (m, 2H), 7.26 (s, 1H), 7.39 ppm (s, br,
1H); 13C NMR (126 MHz, CDCl3): d=21.1, 28.3, 28.4, 81.1, 81.2,
116.1, 116.2, 117.5, 125.7, 129.1, 148.4, 153.1, 153.7, 169.3 ppm; ESI-
MS (pos. detection mode): m/z (%): 389.1(100) [M+Na]+.
1
(yield: 1.37 g, 89%). H NMR (300 MHz, CDCl3): d=1.33–1.38 (t, 3H),
4.27–4.34 (q, 2H), 6.65–6.68 (d, 1H), 7.41 (d, 1H), 7.45–7.49 ppm
(dd, 1H); ESI-MS (pos. detection mode) m/z: 203.0 [M+Na]+, 383.1
[2M+Na]+.
[Ru(bipy)2-dppz-7-acetoxy][PF6]2 (3)
TFA (4 mL) was added slowly at 08C to a stirred solution of 7
(180 mg, 0.49 mmol) in CH2Cl2 (10 mL). After 20 min, the ice bath
was removed and the mixture was stirred at room temperature for
2 h. The solvent and TFA were then evaporated using a high
vacuum pump. The residue was diluted with CH2Cl2 (100 mL) and
washed with a sat. NaHCO3 solution (1ꢂ200 mL). The organic
phase was separated and the aqueous phase was back-extracted
with CH2Cl2 (50 mL). The combined organic layers were dried over
1,2-Diaminobenzyl alcohol (8)
LiAlH4 (442 mg, 11.65 mmol) was added in portions over 10 min to
a stirring solution of 3,4-diaminobenzoic acid ethyl ester (700 mg,
3.88 mmol) in dry THF (35 mL) cooled at 08C. The mixture, which
turned from brown to greenish, was stirred at 608C for 45 min
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Chem. Eur. J. 2014, 20, 1 – 17
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