The Journal of Organic Chemistry
Article
= 1:1) as a white solid. NMR spectral data of product matched those
reported in the literature.29,30
white solid and colorless oil. NMR spectral data of product matched
those reported in the literature.34,38
1
1g: H NMR(300 MHz CDCl3) δ 7.51−7.44 (m, 4H, (E)), 7.37−
1h: 1H NMR(300 MHz CDCl3) δ 8.04 (m, 1H, (E)), 7.89 (m, 2H,
(Z)), 7.59−7.53 (m, 2H, (E)), 7.41−7.20 (m, 9H), 7.13 (d, J = 15 Hz,
0.5H, (E)), 6.71 (d, J = 12 Hz, 1H, (Z)), 6.61 (d, J = 12 Hz, 1H, (Z)),
3.93 (s, 1.5H, (E)), 3.90 (s, 3H, (Z)).
7.32 (m, 2H), 7.29−7.10 (m, 8H), 7.07 (d, J = 16.2 Hz, 1H), 6.98 (d, J
= 17.7 Hz, 1H), 6.92−6.89 (m, 2H), 6.77−6.74 (m, 2H, (Z)), 6.56−
6.48 (m, 2H, (Z)), 3.83 (s, 3H, (E)), 3.79 (s, 3H, (Z)).
4-Cyanostilbene (1i, R = 4-CN). By following the general procedure
for the preparation of compound 1b, the reaction of benzyltriphenyl-
phosphonium chloride (2.994 g, 7.70 mmol) with p-cyanobenzalde-
hyde (0.9183 g, 7.00 mmol) in the presence of lithium hydroxide
monohydrate (0.6547 g, 15.6 mmol) under reflux for 24 h gave 4-
cyanostilbene (1i, 1.380 g, 6.72 mmol, 96%). This compound was
obtained in (E)/(Z) mixture ((E)-isomer/(Z)-isomer = 0.9:1) as a
white solid. NMR spectral data of product matched those reported in
the literature.31,32
2-(3-Methylstyryl)naphthalene (3). To a solution of 3-methyl-
benzonitrile (363.0 mg, 3.90 mmol) in dichloromethane (15 mL) was
added DIBAL (1 M solution in hexane, 3.0 mL, 3.0 mmol) at −80 °C,
and the mixture was stirred for 40 min then for 1.5 h at 0 °C. To the
reaction mixture was added 1 M HCl(aq) (30 mL), and the solution
was extracted with dichloromethane, dried over magnesium sulfate,
and filtered, and the solvent was evaporated under reduced pressure. A
solution of crude product, (2-naphthalenylmethyl)-
triphenylphosphonium bromide (1.2040 g, 2.49 mmol) and lithium
hydroxide monohydrate (215.5 mg, 5.14 mmol) in 2-propanol (50
mL) was stirred under reflux for 3 h. The solvent was evaporated
under reduced pressure, and the residue was separated by column
chromatography (SiO2/hexane) to give 2-(3-methylstyryl)naphthalene
(3, 458.3 mg, 1.88 mmol, 75%). This compound was obtained in (Z)/
(E) mixture as a white solid. The structure of the (E)-isomer was
confirmed because NMR spectral data matched those reported in the
1i: 1H NMR(300 MHz CDCl3) δ 7.66−7.48 (m, 7.5H), 7.42−7.30
(m, 5H), 7.25−7.18 (m, 5.5H), 7.09 (d, J = 18 Hz, 0.9H, (E)), 6.77 (d,
J = 12.0 Hz, 1H, (Z)), 6.57 (d, J = 12.0 Hz, 1H, (Z)).
4-Acetylstilbene (1j, R = 4-COMe). By following the general
procedure for the preparation of compound 1b, the reaction of
benzyltriphenylphosphonium chloride (2.991 g, 7.70 mmol) with p-
acetylbenzaldehyde (1.045 g, 7.05 mmol) in the presence of lithium
hydroxide monohydrate (0.6521 g, 15.5 mmol) under reflux for 2.5 h
gave 4-acetylstilbene (1j, 0.9015 g, 4.06 mmol, 58%). This compound
was obtained in (E)/(Z) mixture ((E)-isomer/(Z)-isomer = 1.2:1) as
a white solid. NMR spectral data of product matched those reported in
the literature.33,34
literature.39 (E)-isomer: white solid; H NMR (300 MHz, CDCl3) δ
1
7.85−7.80 (m, 4H), 7.74 (dd, J = 8.7, 1.8 Hz, 1H), 7.50−7.41 (m,
2H), 7.37 (d, J = 8.7 Hz, 2H), 7.31−7.17 (m, 3H), 7.10 (d, J = 7.2 Hz,
1
1H), 2.40 (s, 3H). (Z)-isomer: colorless liquid; H NMR (300 MHz,
CDCl3) δ 7.88−7.66 (m, 3H), 7.62 (d, J = 8.4 Hz, 1H), 7.44−7.37 (m,
2H), 7.35 (dd, J = 8.4, 1.8 Hz, 1H), 7.13−6.97 (m, 4H), 6.72 (d, J =
12.0 Hz, 1H), 6.63 (d, J = 12.0 Hz, 1H), 2.24 (s, 3H); 13C NMR (75
MHz, CDCl3) δ 137.9, 137.3, 135.0, 133.5, 132.6, 130.8, 130.0, 129.8,
128.2, 128.09, 128.06, 128.01, 127.7, 127.4, 127.0, 126.0 (2C), 125.9,
21.4. Anal. Calcd for C19H16: C, 93.40; H, 6.60. Found: C, 93.35; H,
6.52.
1
1j: H NMR(300 MHz CDCl3) δ 7.96 (d, J = 8.4 Hz, 2.4H, (E)),
7.81 (d, J = 8.4 Hz, 2H, (Z)), 7.61−7.53 (m, 4.8H), 7.40−7.21 (m,
11.8H), 7.13 (d, J = 16.2 Hz, 1.2H, (E)), 6.73 (d, J = 12.3 Hz, 1H,
(Z)), 6.61 (d, J = 12.3 Hz, 1H, (Z)), 2.61 (s, 3.6H, (E)), 2.57 (s, 3H,
(Z)).
4-Nitrostilbene (1k, R = 4-NO2). By following the general
procedure for the preparation of compound 1b, the reaction of
benzyltriphenylphosphonium chloride (2.996 g, 7.70 mmol) with p-
nitrobenzaldehyde (1.058 g, 7.00 mmol) in the presence of lithium
hydroxide monohydrate (0.6556 g, 15.6 mmol) under reflux for 2.5 h
gave 4-nitrostilbene (1k, 1.430 g, 6.35 mmol, 91%). This compound
was obtained in (E)/(Z) mixture ((E)-isomer/(Z)-isomer = 1.3:1) as
a white solid. NMR spectral data of product matched those reported in
the literature.31,35
Optimization for Reaction Conditions of Oxidative Photo-
cyclization of Diarylethenes by NMR (Tables 1, 2, 4, and 5). A 1
mM solution of starting material (cis-stilbene 1a and compound 3 for
Tables 1, 2, 4 and Table 5) in solvent (10 mL) in a 50 mL screw bottle
was irradiated at a distance of 10 cm from a 450 W high-pressure
mercury lamp in the presence of mediator described in the tables.
Reaction conditions are shown in the footnotes of each table. After
filtration of reaction mixture, the solvent was evaporated under
reduced pressure. Yields were estimated by comparing integrals of
1k: 1H NMR(300 MHz CDCl3) δ 8.23 (m, J = 7.2 Hz, 2.6H, (E)),
8.07 (m, J = 8.7 Hz, 2H, (Z)), 7.66−7.54 (m, 5.2H), 7.43−7.12 (m,
13.5H), 6.70 (d, J = 12.3 Hz, 1H, (Z)), 6.58 (d, J = 12.3 Hz, 1H, (Z)).
1-Phenyl-2-(2-thienyl)ethene (1l). By following the general
procedure for the preparation of compound 1b, the reaction of
benzyltriphenylphosphonium chloride (3.001 g, 7.72 mmol) with 2-
thiophenecarboxaldehyde (0.7914 g, 7.06 mmol) in the presence of
lithium hydroxide monohydrate (0.6505 g, 15.5 mmol) under reflux
for 2 h gave 1-phenyl-2-(2-thienyl)ethene (1l, 1.07 g, 5.74 mmol,
81%). This compound was obtained in (E)/(Z) mixture ((E)-isomer/
(Z)-isomer = 1.6:1) as a white solid. NMR spectral data of product
matched those reported in the literature.36,37
1
products in H NMR spectra with dimethylsulfone (0.300 mL of a
stock solution of 10 mM dimethylsulfone in CDCl3 was added to the
NMR sample before measurement) as an internal standard.
In the oxidative photocyclization of compound 3, NMR spectral
data of product matched those reported in the literature.40,41 The ratio
of products was calculated based on the integrals of methyl proton in
1H NMR spectra.
The yield of each experiment is described in Tables 1, 2, 4, and 5.
Preparative Scale Experiments for the Oxidative Photo-
cyclization of Stilbenes and Styrylthiophene (Table 3). Typical
Example: Phenanthrene (2a). To a 1 mM solution of cis-stilbene 1a
in cyclohexane (1300 mL) was added potassium iodide (0.2159 g, 1.30
mmol), and this reaction mixture was irradiated by 450 W high-
pressure mercury lamp. Reaction was monitored by 1H NMR spectra:
1l: 1H NMR(300 MHz CDCl3) δ 7.48−7.45 (m, 3.2H, (E)), 7.37−
7.19 (m, 13.2H), 7.09−6.89 (m, 7.6H), 6.70 (d, J = 12 Hz, 1H, (Z)),
6.58 (d, J = 12 Hz, 1H, (Z)).
1
10 mL of reaction mixture was removed, and H NMR spectrum was
1-(4-Methoxycarbonylphenyl)-2-phenylethene (1h, R = 4-
CO2Me). A solution of benzyltriphenylphosphonium chloride (5.463
g, 14.0 mmol) and methyl 4-formylbenzoate (2.357 g, 14.4 mmol) in
THF (100 mL) was stirred for 30 min at room temperature. To this
reaction mixture was added a solution of sodium methoxide (2.272 g,
42.1 mmol) in THF (100 mL), and the solution was stirred for 40.5 h
at room temperature and then under reflux for 3.5 h. After the solvent
was evaporated under reduced pressure, the residue was dissolved in
dichloromethane. The solution was washed with brine, dried over
magnesium sulfate, and filtered, and the solvent was evaporated under
reduced pressure. The residue was separated by column chromatog-
raphy (SiO2/chloroform) to give 1-(4-methoxycarbonylphenyl)-2-
phenylethene (1h, 1.688 g, 7.08 mmol, 50%). This compound was
obtained in (E)/(Z) mixture ((E)-isomer/(Z)-isomer = 0.5:1) as a
measured after the solvent was evaporated under reduced pressure.
After the starting material was completely consumed (1.75 h), the
solvent was evaporated under reduced pressure, and the residue was
dissolve in dichloromethane. The solution was washed with aqueous
sodium hydrogen sulfite and brine, dried over magnesium sulfate, and
filtered, and the solvent was evaporated under reduced pressure. The
residue was separated by column chromatography (SiO2/hexane) to
give phenanthrene (2a, 0.2228 g, 1.25 mmol, 96%) as a white solid.
The amount of reaction mixture just before workup was decreased to
1290 mL because 10 mL of the reaction solution was removed for
monitoring the reaction. The actual yield should be 97% after
correction. NMR spectral data of product matched those reported in
the literature.42
E
J. Org. Chem. XXXX, XXX, XXX−XXX