Organometallics
Article
(1H, ddd, J 8.3, 7.3, 1.8), 7.08 (1H, ddd, J 7.8, 7.3 1.0), 6.98 (1H, dd, J
8.4, 1.0), 4.63 (1H, t, J 5.6), 3.97 (3H, s), 3.76 (dq, J 9.4, 7.0), 3.67−
3.54 (4H, m), 1.25 (6H, t, J 7.0). HRMS (FTMS+ESI): calcd for
[C14H21NO4+Na]+ 290.1368, found 290.1368. The 13C NMR
spectrum could not be obtained as 8 hydrolyzed to the aldehyde in
the NMR solvent; δH (600 MHz; CDCl3) 9.76 (1H, d, J 0.6), 8.64
(1H, br s), 8.21 (1H, dd, J 7.7, 1.9), 7.51−7.45 (1H, m), 7.09 (1H, t, J
7.6), 7.01 (1H, d, J 8.4), 4.41 (2H, dd, J 4.8, 0.7), 4.03 (3H, d, J 0.6);
δC (151 MHz; CDCl3) 196.97, 165.69, 157.96, 133.45, 132.52, 121.48,
120.70, 111.55, 56.20, 51.15.
2-(2-Methoxyphenyl)oxazole (9) and 2-(2-Methoxy-5-
(methylsulfonyl)phenyl)oxazole (10). Methanesulfonic acid (35
mL) was added cautiously to N-(2,2-diethoxyethyl)-2-methoxybenza-
mide (8) (2.80 g, 11.70 mmol) with stirring. P4O10 (4.50 g, 15.85
mmol) was added with caution, and the mixture was heated to 180 °C
overnight. The mixture was cooled to RT and added dropwise to an
aqueous NaHCO3 solution (300 mL) with stirring. The aqueous phase
(pH 8) was extracted with DCM (3 × 400 mL), and the solvent was
removed in vacuo to leave a thick oil. The residue was purified by
column chromatography (10−20% EtOAc in DCM) to give the
product 9 as a yellow oil (400 mg, 19%): δH (400 MHz; CDCl3) 7.98
(1H, dd, J 8.1, 1.8), 7.76 (1H, d, J 0.8), 7.46 (1H, ddd, J 8.3, 7.4, 1.8),
7.31 (1H, d, J 0.8), 7.04- 7.11 (2H, m), 4.00 (3H, s); δC (151 MHz;
CDCl3) 160.44, 157.67, 138.31, 131.90, 130.41, 128.28, 120.79,
116.61, 112.10, 56.20; HRMS (FTMS+ESI) calcd for
[C10H9NO2+H]+ 176.0712, found 176.0740.
methanol: δH (400 MHz; CDCl3) 11.91 (1H, s), 8.47 (1H, d, J
2.4), 7.91 (1H, dd, J 8.8, 2.4), 7.79 (1H, d, J 0.9), 7.32 (1H, d, J 0.9),
7.23 (1H, d, 8.8), 3.10 (3H, s); δC (101 MHz; CDCl3) 161.39, 160.21,
138.54, 131.68, 131.30, 126.78, 126.56, 118.56, 111.65, 45.01. HRMS
(FTMS+ESI): calcd for [C10H9NO4S]+ 240.0331, found 240.0335.
Iridium Complex 3. IrCl3·3H2O (123 mg, 0.35 mmol) was added to
a stirred solution of 2-phenylpyridine (0.11 mL, 0.77 mmol) in 2-
ethoxyethanol (10 mL). The solution was heated to reflux (135 °C)
overnight. Na2CO3 (300 mg, 2.83 mmol) and 2-(oxazol-2-yl)phenol
(11) (62 mg, 0.38 mmol) were added, and the solution was heated to
reflux overnight before being cooled to RT. Water was added, and the
precipitate was filtered to give a yellow solid. The crude product was
filtered and washed with more water to remove water-soluble
impurities. The product was dried, then washed with hexane and
cold diethyl ether to remove traces of ppy ligand. The product was
obtained as a yellow solid, 3 (200 mg, 87%). Anal. Calcd for
C31H22IrN3O2·0.25CH2Cl2: C, 55.00; H, 3.33; N, 6.17. Found: C,
55.18; H, 3.26; N, 6.02. δH (700 MHz; CDCl3) 8.88 (1H, d, J 5.7,
HA6), 7.99 (1H, d, J 5.8, HC6), 7.85 (1H, d, J 8.2, HC3), 7.80 (1H, d, J
8.2, HA3), 7.72 (1H, dd, J 8.2, 1.9, HF3), 7.67 (1H, td, J 8.1, 1.5, HA4),
7.65 (1H, td, J 8.1, 1.5, HC4), 7.59 (1H, dd, J 7.9, 1.1, HD3), 7.56 (1H,
dd, J 7.6, 1.1, HB3), 7.38 (1H, d, J 1.0, HE2), 7.12 (1H, ddd, J 8.7, 7.0,
1.9, HF5), 7.07 (1H, ddd, J 7.4, 6.0, 1.4, HA5), 6.92 (1H, ddd, J 8.1, 5.9,
1.4, HC5), 6.87 (1H, td, J 7.5, 1.2, HD4), 6.86 (1H, td, J 7.4, 1.2, HB4),
6.80−6.75 (2H, m, HF6+D5), 6.73 (1H, dt, J 7.3, 1.1, HB5), 6.42 (1H,
ddd, J 7.9, 6.9, 1.1, HF4), 6.36 (1H, d, J 7.6, HB6), 6.28 (1H, d, J 7.6,
HD6), 6.20 (1H, d, J 1.0, HE1); δC (151 MHz; CDCl3) 169.22 (CC2),
168.10 (CA2), 167.20 (CF1), 158.67 (CE3), 152.67 (CD1), 149.07 (CA6)
148. 72 (CB1), 148.67 (CC6), 144.87 (CB2), 144.83 (CD2), 137.49
(CE2), 136.91 (CA4), 136.74 (CC4), 133.20 (CB6), 132.56 (CF5), 132.48
(CD6), 129.69 (CB5), 129.58 (CD5), 127.39 (CF3), 126.64 (CE1),
125.53 (CF6), 124.18 (CB3), 124.10 (CD3), 122.07 (CA5) 121.80 (CC5),
120.79 (CD4), 119.02 (CB4), 118.73 (CC3), 118.25 (CA3), 113.34
(CF4), 110.94 (CF2). HRMS (FTMS+ESI): calcd for [C31H22N3O4191Ir
+H]+ 660.1396, found 660.1406.
Also isolated was a second fraction: 2-(2-methoxy-5-(methyl-
sulfonyl)phenyl)oxazole (10) (538 mg, 18%): δH (400 MHz;
CDCl3) 8.54 (1H, dd, J 2.4, 0.8), 8.01 (1H, ddd, J 8.8, 2.4, 0.8),
7.78 (1H, d, J 0.8), 7.33 (1H, s), 7.18 (1H, d, J 8.8), 4.07 (3H, s), 3.09
(3H, s); δC (151 MHz; CDCl3) 161.29, 158.31*, 139.10, 131.21,
130.18, 128.69, 117.36*, 112.49, 56.85, 44.94 (* denotes carbons
identified from the HMBC spectrum). One carbon is not observed due
to low solubility. HRMS (FTMS+ESI): calcd for [C11H11NO4S+H]+
254.0487, found 254.0471.
2-(Oxazol-2-yl)phenol, 11. BBr3 (0.65 mL, 6.87 mmol) was added
dropwise to a stirred solution of 2-(2-methoxyphenyl)oxazole (9)
(400 mg, 2.28 mmol) in DCM (10 mL, dry) over an ice bath. The
suspension was stirred at RT overnight before the reaction was
quenched with water (CAUTION). The solid formed, presumed to be
(2-(2-hydroxyphenyl)oxazol-3-ium bromide) was filtered off and
suspended in DCM. This was then washed with aqueous Na2CO3
to neutralize the salt. The organic phase was collected, and the
aqueous phase was washed with further DCM (3 × 50 mL). The
organic phases were combined, dried over MgSO4, and filtered. The
solvent was removed in vacuo to give an oil, 2-(oxazol-2-yl)phenol
(11) (250 mg, 68%): δH (700 MHz; CDCl3) 11.20 (1H, s), 7.84 (1H,
dd, J 7.8, 1.7), 7.69 (1H, t, J 0.9), 7.39−7.34 (1H, m), 7.24 (1H, d, J
1.0), 7.08 (1H, dd, J 8.3, 1.2), 6.95 (1H, td, J 7.5, 1.0); δC (176 MHz;
CDCl3) 161.78, 157.35, 137.49, 132.47, 126.51, 126.08, 119.52,
117.31, 111.25. HRMS (FTMS+ESI): calcd for [C9H7NO2+H]+
162.0555, found 162.0542.
4-(Methylsulfonyl)-2-(oxazol-2-yl)phenol, 12. BBr3 (0.61 mL, 6.37
mmol) was added dropwise to a stirred solution of 2-(2-methoxy-5-
(methylsulfonyl)phenyl)oxazole (10) (538 mg, mmol) in DCM (10
mL, dry) over an ice bath. The suspension was stirred at RT overnight
before the reaction was quenched with water (CAUTION). The solid
formed, presumed to be 2-(2-hydroxy-5-(methylsulfonyl)phenyl)-
oxazol-3-ium bromide, was filtered off and suspended in DCM. This
was then washed with aqueous Na2CO3 to neutralize the salt. The
organic phase was collected, and the aqueous phase was washed with
further DCM (3 × 50 mL). The organic phases were combined, dried
over MgSO4, and filtered. TLC revealed a mixture of starting material
and product; the crude mixture was redissolved in DCM and extracted
with aqueous NaOH solution (3 × 50 mL, 1 M). The aqueous phases
were combined, acidified to pH 6 with concentrated HCl, and re-
extracted with DCM (4 × 100 mL). The organic phase was dried over
MgSO4, the solvent was removed, and the residue was purified by silica
plug (EtOAc) to give a white solid, 4-(methylsulfonyl)-2-(oxazol-2-
yl)phenol (12) (200 mg, 39%), which was recrystallized from
Iridium Complex 4. IrCl3·3H2O (236 mg, 0.67 mmol) was added to
a stirred solution of 2-phenylpyridine (0.21 mL, 1.47 mmol) in 2-
ethoxyethanol (10 mL). The solution was heated to reflux (135 °C)
overnight. Na2CO3 (354 mg, 3.34 mmol) and 4-(methylsulfonyl)-2-
(oxazol-2-yl)phenol (12) (200 mg, 0.84 mmol) were added, and the
solution was heated to reflux overnight before being cooled to RT.
Water was added and the precipitate was filtered to give a yellow solid.
The crude material was purified by column chromatography (10%
EtOAc in DCM) to give the product as a yellow solid. Fractions
containing product 4 contaminated with unreacted ppy were
combined, the solvent was then removed, and the solid was washed
with hexane to give additional product 4 (combined yield: 281 mg,
57%). Anal. Calcd for C32H24IrN3O4S: C, 52.02; H, 3.27; N, 5.69.
Found: C, 51.84; H, 3.61; N, 5.27. δH (400 MHz; CDCl3) 8.75 (1H,
ddd, J 5.8, 1.5, 0.7), 8.38 (1H, d, J 2.6), 7.96 (1H, d, J 5.7, 1.5, 0.7),
7.91 (1H, d, J 8.1), 7.87 (1H, d, J 8.1), 7.75 (1H, td, J 7.6, 1.7), 7.73
(1H, td, J 7.5, 1.6), 7.60 (1H, td, J 8.4, 1.1), 7.57 (1H, dd, J 9.2, 2.6),
7.49 (1H, d, J 1.0), 7.14 (1H, ddd, J 7.3, 5.7, 1.4), 7.01 (1H, ddd, J 7.4,
5.8, 1.5), 6.93 (1H, td, J 7.5, 1.2), 6.92 (1H, td, J 7.5, 1.2), 6.82 (1H, d,
J 9.2), 6.79 (1H, td, J 6.16, 1.2), 6.76 (1H, td, J 7.4, 1.4), 6.83−6.77
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Organometallics XXXX, XXX, XXX−XXX