A R T I C L E S
Dietrich-Buchecker et al.
glass and the filtrate evaporated to dryness to give 14.9 g of crude 9,
which crystallized upon cooling. This crude solid was filtered over a
sintered glass and washed with cold C6H6 and subsequently with cold
Et2O, affording 5.93 g (17.7 mmol) of pure 9. An additional 1.0 g (2.98
mmol) of 9 could be obtained by column chromatography on silica
gel (eluent: CH2Cl2, 1% MeOH). Overall yield: 82% (6.93 g, 20.68
mmol), colorless solid (mp 187-189 °C). 1H NMR (200 MHz,
CDCl3): 9.23 (dd, 1H, H9, J1 ) 4.4 Hz, J2 ) 1.8 Hz), 8.29 (d, 1H, H4,
J ) 8.4 Hz), 8.25 (dd, 1H, H7, J1 ) 8.4 Hz, J2 ) 1.8 Hz), 8.22 (d, 1H,
was stirred overnight and then allowed to warm to room temperature
before hydrolysis with 100 mL of a 4 M HCl solution. The two layers
were separated, and ether was evaporated. The solid was taken up in
100 mL of aqueous Na2CO3 (2 M) and 100 mL of Et2O. The two layers
were separated again. The aqueous layer was acidified and extracted
three times with 100 mL of Et2O. The combined organic layers were
dried over MgSO4 to yield the free acid boronic derivative as a white
solid (0.86 g). This solid was dissolved in 30 mL of benzene with 0.31
g of 2,2-dimethyl-1,3-propanediol (1 equiv) and a catalytic amount of
p-toluenesulfonic acid. This mixture was heated under reflux for 2 h.
Evaporation of the solvent gave 13 as a white solid (1.06 g, 70% yield).
1H NMR (200 MHz, CDCl3): δ 7.78 (d, J ) 8.4 Hz, 2H), 7.44 (d, J
) 9.1 Hz, 2H), 6.96 (d, J ) 9.1 Hz, 2H), 6.91 (d, J ) 8.4 Hz, 2H),
3.77 (s, 4H), 1.03 (s, 6H). 13C NMR (200 MHz, CDCl3): δ 156.1,
153.0, 135.7, 132.7, 129.7, 120.8, 117.8, 116.0, 72.3, 31.9, 21.9. Anal.
Calcd for C17H18O3BBr: C, 56.55; H, 5.03. Found: C, 56.50; H, 4.93.
MS (EI): m/z 360.1 (M+).
H0-1, J ) 8.2 Hz), 8.04 (d, 1H, H3, J ) 8.4 Hz), 7.78 (AB, 2H, H5,6,
J ) 10.2 Hz), 7.66 (d, 2H, Hm-1, J ) 8.8 Hz). Anal. Calc for C18H11N2-
Br: C, 64.50; H, 3.31; N, 8.36. Found: C, 64.75; H, 3.20; N, 8.66. MS
(EI): m/z found 335, calc 335.2.
Preparation of 2,9-Bis(p-bromophenyl)-1,10-phenanthroline (10).
A 25 mL sample of an etheral solution of p-bromophenyllithium
(prepared as above from 2.9 g, 12 mmol of p-dibromobenzenze, and
11 mmol of n-Buli) was slowly added, by means of a double-ended
needle, to a degassed suspension of 9 (2.01 g, 6 mmol) in 70 mL of
anhydrous Et2O maintained at 2 °C. The resulting dark purple solution
was stirred during three further hours at 3 °C. After hydrolysis at 0
°C, decantation, three extractions with CH2Cl2, and rearomatization with
8.0 g of MnO2, 3.05 g of a crude mixture was obtained as a pale yellow
solid. Column chromatography of the latter over silica gel (eluent: CH2-
Cl2, 0.5% MeOH) afforded pure 10 (2.6 g, 5.30 mmol, 88% yield) as
a colorless solid (mp 219-221°C). 1H NMR (200 MHz, CDCl3): 8.33
(d, 4H, Ho-1, J ) 8.8 Hz), 8.33 (d, 2H, H4,7, J ) 8.8 Hz), 8.12 (d, 2H,
Compound 7. To a degassed solution of 4-bromopyridine hydro-
chloride (14, 0.65 g, 3.36 mmol) and [Pd(PPh3)4] (110 mg, 0.17 mmol)
in 80 mL of toluene were added 30 mL of a degassed solution of 2 M
aqueous Na2CO3 and a solution of 13 (1.21 g, 3.36 mmol) in 20 mL of
toluene under argon. It is very important to respect the following
sequence in the additions: (1) 4-iodopyridine in toluene, (2) vacuum/
Ar three times, (3) addition of the catalyst, (4) vacuum/Ar three times,
(5) addition of the degassed solution of Na2CO3, (6) addition of the
degassed solution of the boronic ester. After 2 h of reflux, the reaction
mixture was allowed to cool to room temperature. The solvent was
evaporated, and the crude product was chromatographed over alumina
using hexane-dichloromethane as the eluents. Compound 7 was
obtained (CH2Cl2) as a white solid (0.92 g, 80% yield).
H3,8, J ) 8.4 Hz), 7.81 (s, 2H, H5,6), 7.73 (d, 4H, Hm-1, J ) 8.8 Hz).
Anal. Calc for C24H14N2Br2: C, 58.81; H, 2.88; N, 5.71. Found: C,
59.04; H, 2.79; N, 5.74. MS (EI): m/z found 490, calc 490.2.
2,9-Bis[4′-(4-pyridyl-4-phenoxy)biphenyl]-1,10-phenanthroline (1b).
Compound 8 (400 mg, 0.98 mmol), LiCl (170 mg, 4.00 mmol), and
[PdCl2(PPh3)2] (30 mg, 0.04 mmol) were combined in toluene (50 mL)
under argon. 2,9-Bis(4-bromophenyl)-1,10-phenanthroline (10, 196 mg,
0.40 mmol) in toluene (30 mL) was added to the mixture, and the
mixture was stirred at 120 °C. After 12 h, the product was extracted
with CHCl3 and purified by column chromatography (CHCl3-MeOH,
20:1) to give 1b as colorless crystals (150 mg, yield 45%). Mp: 249-
4-Boronic Ester-4′-pyridyldiphenyl Ether (16). Bis-pinacolato
diboron (15, 0.63 g, 2.48 mmol), 7 (0.74 g, 2.26 mmol), KOAc (0.67
g, 6.78 mmol), and Pd(dppf)Cl2‚CH2Cl2 (55 mg, 0.07 mmol) were
dissolved in freshly distilled dioxane (15 mL). The mixture was stirred
under argon at 80 °C for 14 h. After the solution had cooled to room
temperature, 20 mL of water was added. The dioxane was evaporated
under vacuum, and 100 mL of CH2Cl2 was added. The organic layer
was dried over MgSO4, filtered, and evaporated. The crude was then
purified on a short silica column to give a black oil (yield 95%). The
1H NMR was very nice, and the product was used without other
purification. 1H NMR (200 MHz, CDCl3): δ 8.65 (d, J ) 6.2 Hz, 2H),
7.83 (d, J ) 8,6 Hz, 2H), 7.62 (d, J ) 8.6 Hz, 2H), 7,49 (d, J ) 6.2
Hz, 2H), 7.12 (d, J ) 8.6 Hz, 2H), 7.05 (d, J ) 8.6 Hz, 2H), 1.36 (s,
12H).
1
250 °C. H NMR (500 MHz, CDCl3): δ 8.66 (d, J ) 6.1 Hz, 4H,
Hm-4), 8.59 (d, J ) 8.3 Hz, 4H, Ho-1), 8.35 (d, J ) 8.3 Hz, 2H, H4,7),
8.22 (d, J ) 8.3 Hz, 2H, H3,8), 7.84 (d, J ) 8.3 Hz, 4H, Hm-1), 7.83 (s,
2H, H5,6), 7.75 (d, J ) 8.4 Hz, 4H, Ho-2), 7.65 (d, J ) 8.7 Hz, 4H,
Hm-3), 7.50 (d, J ) 6.1 Hz, 4H, Ho-4), 7.19 (d, J ) 8.7 Hz, 4H, Ho-3),
7.18 (d, J ) 8.4 Hz, 4H, Hm-2). 13C NMR (125 MHz, CDCl3): δ 156.3,
154.2, 153.9, 147.3, 146.0, 143.7, 139.0, 135.9, 134.9, 134.1, 130.2,
126.3, 126.2, 125.9, 125.8, 125.0, 123.8, 119.3, 118.0, 117.5, 116.8.
IR (KBr, cm-1): 1596, 1506, 1484, 1245, 835, 818, 798, 418. Anal.
Calcd for C58H38O2N4‚H2O: C, 82.84; H, 4.74; N, 6.66. Found: C,
82.86; H, 4.68; N, 6.57.
Ligand 1b. To a degassed solution of 2,9-bis(4-bromophenyl)-
1,10-phenanthroline 10 (0.45 g, 0.91 mmol) and [Pd(PPh3)4] (84 mg,
0.07 mmol) in 30 mL of toluene were added 9 mL of a degassed
solution of 2 M aqueous Na2CO3 and a solution of 16 (0.75 g, 2.00
mmol) in 10 mL of toluene under argon. After 17 h of reflux, the
reaction mixture was allowed to cool to room temperature and a
precipitate appeared. It was filtered off and washed with water, toluene,
and ether to yield 0.60 g of the ligand 1b (yield 80%).
4-Bromo-4′-iododiphenyl Ether (12). 4-Bromodiphenyl ether (11,
5 g, 20 mmol) was stirred in 100 mL of acetic acid. ICl (4.9 g, 30
mmol) in 30 mL of acetic acid was added dropwise to the solution at
room temperature. When the addition was over, the solution was heated
at reflux for 2 h. The acetic acid was then evaporated. The solid was
taken up in CH2Cl2. The solution was decolorized with 10% Na2S2O3,
and Na2CO3 was added until pH ) 7. The organic layer was also washed
with water. After extracting with CH2Cl2, drying over MgSO4,
evaporating the solvent, and recrystallizing in hexane, the product was
obtained as a white solid (7.3 g, yield 99%). 1H NMR (200 MHz,
CDCl3): δ 7.63 (d, J ) 9.0 Hz, 2H), 7.45 (d, J ) 8.8 Hz, 2H), 6.88 (d,
J ) 9.0 Hz, 2H), 6.88 (d, J ) 8.8 Hz, 2H).
4-Bromo-4′-diphenyl Ether Boronic Ester (13). A solution of 1.58
g of 12 (4.22 mmol) in 70 mL of diethyl ether was degassed and cooled
to -78 °C. Then, 0.63 mL of TMEDA (4.22 mmol) were added,
followed by 2.7 mL of n-butyllithium in hexane (4.64 mmol). After
stirring for 3 h at -78 °C, a degassed solution of trimethylborate (1.68
g, 17 mmol) in 15 mL of dry Et2O was added via cannula. The reaction
[Cu(1b)2]‚PF6 (17b). Ligand 1b (33.0 mg, 0.04 mmol) and Cu(CH3-
CN)4‚PF6 (7.5 mg, 0.02 mmol) were combined in DMF (1 mL) at room
temperature under argon. The mixture was stirred for 15 min to give
a clear dark red solution. Cu(I) complex 17b was precipitated as a purple
powder by adding a large amount of diethyl ether. Yield: 93%. Mp:
1
191-192 °C dec. H NMR (500 MHz, DMF-d7): δ 9.27 (d, J ) 8.4
Hz, 4H, H4,7), 8.66 (d, J ) 8.4 Hz, 4H, H3,8), 8.62 (s, 4H, H5,6), 8.48
(d, J ) 8.0 Hz, 8H, Hm-3), 8.26 (d, J ) 7.7 Hz, 8H, Ho-1), 7.86 (d, J
) 8.2 Hz, 8H, Ho-2), 7.73 (d, J ) 8.0 Hz, 8H, Ho-3), 7.69 (d, J ) 8.2
Hz, 8H, Hm-2), 7.46 (d, J ) 7.7 Hz, 8H, Hm-1). 13C NMR (125 MHz,
DMF-d7): δ 158.7 (Cq), 157.1 (Cq), 156.7 (Cq), 144.1 (Cq), 140.9
(Cq), 138.44 (CH4,7), 138.39 (Cq), 135.7 (Cq), 129.4 (CHo-1), 129.2
(CHo-2), 129.1 (CHm-3), 127.2 (CH5,6), 126.0 (CHm-1), 125.3 (CH3,8),
9
5724 J. AM. CHEM. SOC. VOL. 125, NO. 19, 2003