H. China, et al.
CatalysisTodayxxx(xxxx)xxx–xxx
2.2. Optimization of reaction conditions for p-quinone synthesis
To a suspension of 1-methoxynaphthalene 1 (0.1 mmol, 15.8 mg),
organoiodine catalyst (1.0 equiv., 0.10 of IBX, IBA, or 2-IB), Oxone®,
and 1,4-dinitrobenzene (0.05 mmol, 8.4 mg) as an internal standard in
MeCN (1.25 mL) was added water (1.25 mL). If necessary, V2O5 (10 mol
%, 0.01 mmol, 1.8 mg) and/or 10 M H2O2 (5.0 equiv., 0.50 mol, 50 μL)
were added to the mixture. After the mixture was stirred at room
temperature, the organic layer was extracted with CDCl3 (2.5 mL). The
yields of 2 were determined by qNMR analysis of the extracts.
2.3. Effect of the water content
1,3-Dimethoxybenzene 5 (0.1 mmol, 13.8 mg), 2-IB (1.0 equiv.,
0.1 mmol, 24.8 mg), Oxone® (0.3 mmol, 184 mg), and 1,4-dini-
trobenzene (0.05 mmol, 8.4 mg) as an internal standard was suspended
by addition of a mixed solvent of MeCN/water (various ratio, total
volume: 1.0 mL). After the mixture was stirred at room temperature for
1.5 h, the organic layer was extracted with CDCl3 (1 mL). The yields of
6 were determined by qNMR analysis of the extracts.
Scheme 1. General method of p-quinone synthesis from phenols and anisoles.
2.4. General procedure for the synthesis of p-quinones in the presence of
Oxone® and 2-IB
To a suspension of anisole derivative (1.0 mmol), 2-IB (1.0 mmol,
248 mg), and Oxone® (3.0 mmol, 1.844 g) in MeCN (4 mL) was added
water (6 mL). The mixture was stirred at room temperature until
complete consumption of the starting material (confirmed by TLC
analysis). Then, the insoluble material was removed by filtration with
CH2Cl2 and then the organic layer was extracted with CH2Cl2 (50 mL) at
twice. The extract was washed with a saturated NaHCO3 aqueous so-
lution (100 mL) and then filtered through filter paper for dehydration.
After the solvent was removed by evaporation, the desired product was
purified by flash silica gel chromatography with appropriate solvent.
2: 1H NMR (400 MHz, CDCl3) : δ 6.98 (2H, s), 7.76 (2H, m), 8.08
(2H, m) ppm. 13C NMR (100 MHz, CDCl3) : δ 126.4, 131.9, 133.9,
Scheme 2. p-Quinone synthesis from a monomethoxyarene using a combina-
tion of Fe catalyst with persulfate oxidant.
3: 1H NMR (400 MHz, CDCl3) : δ 6.45 (1H, d, J =10.1 Hz), 7.38
(1H, d, J =7.8 Hz), 7.46 (1H, d, J =10.1 Hz), 7.52 (1H, td, J = 7.8,
0.9 Hz), 7.67 (1H, td, J = 7.8, 1.4 Hz), 8.12 (1H, dd, J = 7.8, 1.4 Hz)
ppm. 13C NMR (100 MHz, CDCl3) : δ 127.9, 129.9, 130.2, 130.9, 131.6,
134.8, 135.9, 145.4, 178.9, 180.9 ppm. [38]
6: 1H NMR (400 MHz, CDCl3) : δ 3.85 (3H, s), 5.96 (1H, s), 6.73 (2H,
s) ppm. 13C NMR (100 MHz, CDCl3) : δ 56.3, 107.7, 134.5, 137.3, 158.6,
Scheme 3. p-Quinone synthesis from methoxyarenes using Oxone® and an or-
ganoiodine catalyst.
8: 1H NMR (400 MHz, CDCl3) : δ 3.92 (3H, s), 6.19 (1H, s), 7.69-
7.79(2H, m), 8.08 (1H, dd, J = 7.3, 1.8 Hz), 8.13 (1H, dd, J = 7.3,
1.4 Hz) ppm. 13C NMR (100 MHz, CDCl3) : δ 56.4, 109.9, 126.2, 126.7,
131.0, 132.0, 133.4, 134.4, 160.4, 180.1, 184.8 ppm. [39]
9: 1H NMR (400 MHz, CDCl3) : δ 4.03 (3H, s), 5.99 (1H, s), 7.59 (1H,
td, J = 7.8, 1.4 Hz), 7.70 (1H, td, J = 7.8, 1.4 Hz), 7.87 (1H, dd,
J = 7.8, 0.9 Hz), 8.13 (1H, dd, J = 7.8, 0.9 Hz) ppm. 13C NMR
(100 MHz, CDCl3) : δ 56.8, 103.1, 124.8, 129.1, 130.4, 131.6, 132.0,
135.0, 168.7, 179.4 ppm. [40]
11a: 1H NMR (400 MHz, CDCl3) : δ 3.95 (3H, s), 6.92 (1H, s), 6.93
(1H, s), 7.21 (1H, dd, J = 8.7, 2.8 Hz), 7.48 (1H, d, J =2.8 Hz), 8.01
(1H, d, J =8.7 Hz) ppm. 13C NMR (100 MHz, CDCl3) : δ 55.9, 109.6,
120.5, 125.4, 128.9, 133.9, 138.2, 139.0, 164.1, 184.1, 185.1 ppm.
Scheme 4. Oxidation of 1-methoxynaphthalene 1 using Oxone®.
multiplet (m). Data are reported as follows: Chemical shift (number of
protons, multiplicity, coupling constants). qNMR analysis was per-
formed with 40 s of reduction delay time, 6 ppm of offset value, and
6 ppm of sweep value in the presence of 1,4-dinitrobenzene as an in-
ternal standard in CDCl3. Substrates 7a [32], 7b [33], 10a [34], and
10b [35,36] were prepared from 1,2-naphthalenediol, 1,3-naphthale-
nediol, 1,7-naphthalenediol, and 5-amino-1-naphthol, respectively.
11b: 1H NMR (400 MHz, CDCl3) : δ 2.30 (3H, s), 6.91 (1H, d, J
=10.1 Hz), 6.95 (1H, d, J =10.6 Hz), 7.72(1H, t, J =8.0 Hz), 7.81 (1H,
dd, J = 7.8, 1.4 Hz), 9.07 (1H, dd, J = 8.2, 0.9 Hz), 11.85 (1H, brs)
ppm. 13C NMR (100 MHz, CDCl3) : δ 25.7, 115.9, 121.9, 126.0, 132.1,
135.7, 137.9, 139.9, 141.3, 169.9, 184.4, 189.0 ppm. [42]
14a: 1H NMR (400 MHz, CDCl3) : δ 2.07 (3H, d, J =1.4 Hz), 3.82
(3H, s), 5.93 (1H, s), 6.56 (1H, q, J =1.4 Hz) ppm. 13C NMR (100 MHz,
2