Konosonoks et al.
removed under vacuum and the residue was purified using a
silica gel column eluted with 10% ethyl acetate in hexane to
give of 3-o-tolyl-3H-isobenzofuran-1-one (5) as a white solid,
which was recrystallized from hexane/ethyl acetate to yield
colorless needles (26 mg, 79%). The melting point,34 IR and
NMR spectra35 of this compound match those in the literature.
Mp: 112-113.5 °C (lit.34 113 °C). IR (KBr): 2957, 1760, 1464,
1287, 1212, 1065, 946, 741 cm-1. 1H NMR (250 MHz, CDCl3):
δ 2.50 (s, 3H), 6.69 (s, 1H), 6.92 (d, 1H), 7.10-7.17 (m, 1H),
7.27 (m, 2H), 7.34 (m, 1H), 7.55-7.71 (m, 2H), 7.98 (d, 1H)
ppm.
Photooxidation of 3. In a 100 mL Pyrex flask, 3 (0.179 g,
0.70 mmol) was dissolved in 2-propanol (70 mL), and the
solution was saturated with oxygen at 0 °C for 30 min and
photolyzed for 5 h via a Pyrex filter; the reaction was followed
by GC. The reaction mixture was evaporated and the residue
was recrystallized from ethyl acetate to give (0.127 g, 71%
yield) of methyl 2-(3-oxo-1,3-dihydro-isobenzofuran-1-yl)-ben-
zoic acid methyl ester, 8. Recrystallization from ethyl acetate
yielded 8 as colorless needles. The melting point for this
compound matches that reported.35 The crystals of 8 were
triclinic P-1, R1 ) 0.0639, wR2 ) 0.1145. Mp: 156-157 °C
(lit.36 156 °C). IR (KBr): 3494, 2950, 1759, 1724, 1257, 1064,
986, 750 cm-1. 1H NMR (250 MHz, CDCl3): δ 4.01 (s, 3H), 7.25
(m, 1H), 7.37-7.63 (m, 5H), 7.96 (d, 1H), 8.07 (d, 1H) ppm.
10% ethyl acetate in hexane to give recovered starting material
(66 mg, 0.26 mmol, 26%), 1,2-bis(2-methylphenyl)-1,2-bis(4-
carbmethoxyphenyl)-1,2-ethanediol (7), a white crystalline
compound (33 mg; 0.065 mmol, 13%), and 4-(2-methyl-ben-
zoyl)-benzoic acid methyl ester (6) (108 mg, 0.42 mmol, 42%)
as an oil. The crystals of 7 were monoclinic C2/c, R1 ) 0.0483,
wR2 ) 0.133
Data for 6. IR (KBr): 3460, 1723, 1281 cm-1. 1H NMR (250
MHz, CDCl3): δ 2.28 (s, 3 H), 3.90 (s, 3 H), 6.05 (s, 1 H), 7.24-
7.17 (m, 4 H), 7.41 (d, 8 Hz, 2 H), 7.99 (d, 8 Hz, 2 H) ppm. 13
C
NMR (60 MHz, CDCl3): δ 19.4 52.2, 73.2, 125.6, 126.4, 126.8,
127.0, 128.0, 128.6, 129.3, 129.8, 130.9, 135.7, 141.0, 148.1,
167.1 ppm. MS (EI) m/z (relative intensity): 256 (M+, 4), 241
(14), 225 (12), 197 (10), 179 (54), 163 (32), 152 (9), 137 (100),
119 (42), 105 (38), 91 (56), 77 (46), 65 (20). HRMS: m/z calcd
for C16H17O3, [M + H]+ 257.1178, found 257.1248.
Data for 7. Mp: 139-142 °C. IR (KBr): 3540, 1724, 1434,
1281, 1111 cm-1. 1H NMR (250 MHz, CDCl3): δ 1.92 (s, 6 H),
3.10 (s, 2 H), 3.90 (s, 6 H), 6.80 (d, 8 Hz, 4 H), 7.00-6.94 (m,
2 H), 7.15-7.08 (m, 4 H), 7.75 (d, 8 Hz, 4 H), 7.90 (d, 8 Hz, 2
H) ppm. 13C NMR (60 MHz, CDCl3): δ 22.4, 52.3, 84.5, 124.0,
127.6, 128.0, 128.1, 129.1, 131.5, 133.3, 138.0, 141.3, 148.2,
167.0 ppm. HRMS: m/z calcd for C32H31O6, [M + H]+ 511.2121,
found 511.2048.
Photolysis of 10. A degassed solution of 10 (3 mg, 0.01
mmol) in 2-propanol (1 mL) was irradiated via Pyrex sleeve
for 30 min. The solvent was evaporated and the residue was
Ester 3 (300 mg, 1.2 mmol) was dissolved in benzene, and
the resulting 1 × 10-2 M solutions were placed in 15 mm ×
180 mm Pyrex test tubes and purged with oxygen. The
solutions were then irradiated (Pyrex sleeve) for 30 min, thus
keeping the conversion deliberately low. The solutions were
evaporated, and the reaction mixture was separated by silica
gel column chromatography to give unreacted 3 (120 mg, 0.48
mmol 40% recovery), 8 (22 mg, 0.08 mmol, 7%), and a mixture
of spiro(2,3-benzodioxin-1-isobenzofuran-1-one), 9, and 2-(2-
formyl-benzoyl)-benzoic acid, methyl ester, 10, (39 mg) in a
1
dissolved in CDCl3. H NMR of the reaction mixture showed
clean formation of 8 and no remaining starting material.
Photolysis of a Mixture of 3 and Maleic Anhydride.
An argon-saturated solution of 3 (0.025 M) in benzene and
maleic anhydride (0.25 M) was irradiated via Pyrex sleeve for
24 h. GC analysis showed no product formation. An argon-
saturated solution of 3 (0.025 M) and maleic anhydride (0.25
M) in methanol was irradiated for 8 h. GC analysis of the
reaction mixture showed only formation of photoproduct 5.
Quantum Yields. Quantum yields for photoreduction and
photooxidation of 3 were determined, both for the disappear-
ance of the starting material and formation of products 5 and
8. 2-Propanol was purified and dried prior to use.15 The mole-
to-area ratio response of the GC was calibrated for compounds
3, 5, and 8 and hexadecane. Photolyses were carried out to
about 5% conversion in argon-saturated solutions and to 10%
conversion in oxygen-saturated solutions. Solutions of 3 (0.05
M) and hexadecane (0.005 M) were irradiated on a merry-go-
round apparatus using a 450-W medium-pressure mercury arc
lamp and potassium chromate filter to isolate the 3130-Å line.
Solutions were analyzed on a Shimadzu GC-17A gas chro-
matograph equipped with a 15 m × 0.25 mm column with
temperature programming between 65 and 320 °C. 1-(4-
Methoxy-phenyl)-butan-1-one (ΦII ) 0.095 in benzene) was
used as an actinometer.13 Each quantum yield was measured
three times and averaged.
1
2:3 ratio according to H NMR. This mixture was separated
by column chromatography to yield aldehyde 10 (20 mg, 0.08
mmol, 6% yield) as colorless crystals that decomposed upon
standing and peroxide 9 (5 mg, 0.02 mmol, 2% yield) as a
colorless oil. The crystals of 10 were triclinic P-1, R1 ) 0.0382,
wR2 ) 0.0994 (see Supporting Information).
Data for 9. IR (chloroform): 1784, 1215 cm-1. 1H NMR (250
MHz, CDCl3): δ 5.15 (d, 16 Hz, 1H), 5.72 (d, 16, 1H), 6.79-
8.02 (m, 8H) ppm. 13C NMR (60 MHz, CDCl3): δ 72.2, 77.4,
122.7, 124.2, 124.6, 125.9, 127.0, 128.1, 129.3, 129.8, 132.0,
133.3, 135.0, 144.9, 187.8 ppm. HRMS: m/z calcd for C15H9O4
[M - H]+ 253.0511, found 253.0502.
Data for 10. Mp: 101-103 °C. IR (chloroform): 1720, 1697,
1
1671, 1286 cm-1. H NMR (250 MHz, CDCl3) δ 3.64 (s, 3H),
7.24-8.02 (m, 8H), 10.43 (s, 1H) ppm. 13C NMR (60 MHz,
CDCl3) δ: 52.6, 128.5, 129.0, 130.0, 130.2, 130.8, 132.2, 132.4,
132.5, 137.2, 141.0, 166.6, 192.7, 197.3 ppm. HRMS: m/z calcd
for C16H12O4Na [M + Na]+ 291.0633, found 291.0660.
Acknowledgment. We thank Professor M. S. Platz
at The Ohio State University for allowing us to use some
of his instruments. C.B. thanks NSERC for funding.
A.K. thanks University of Cincinnati for URC Funding.
X-ray crystal structure data was collected through the
Ohio Crystallographic Consortium, funded by the Ohio
Board of Regents 1995 Investment Fund (CAP-075)
located at the University of Toledo, Instrumentation
Center in A&S, Toledo, OH 43606 and at the University
of Cincinnati Smart6000 diffractometer, which was
funded by NSF-MRI grant CHE-0215950.
Photolysis of 3 in CH3OD. An argon-saturated solution
of 3 (13 mg, 0.05 mmol) in CH3OD (2 mL) was irradiated via
Pyrex filter for 2 h. The solvent was removed under vacuum,
1
and the residue was dissolved in CDCl3 and analyzed by H
NMR spectrometer. The o-methyl singlet at 3.61 ppm was
1
absent in the in the H NMR spectrum.
Photolysis of 4. A solution of methyl 4-(2-methyl benzoyl)-
benzoic acid, methyl ester (258 mg, 1.01 mmol) in argon-
saturated 2-propanol (20 mL) was irradiated via Pyrex filter
for 18 h. GC analysis of the reaction mixture indicated
formation of two photoproducts and some remaining starting
material. The solvent was removed under vacuum, and the
reaction mixture was separated on a silca column eluted with
Supporting Information Available: X-ray structures of
1
7, 8, and 10 in CIF format; H NMR spectra of 4, 6, 7, 8, and
10; Cartesian coordinates, no. of imaginary frequencies, and
total energy of 3, 3Z, and 3E; and preparation of 3 and 4. This
material is available free of charge via the Internet at
(34) Okada, K.; Tanaka, M. J. Chem. Soc., Perkin Trans. 1 2002,
23, 2704.
(35) Fieser, L. F. J. Am. Chem. Soc. 1931, 53, 3546.
(36) Armarego W. L. F.; Perrin D. D. Purification of Laboratory
Chemicals, 4th ed.; Butterworth-Heinemann: Oxford, Boston, 1996.
JO048055X
2770 J. Org. Chem., Vol. 70, No. 7, 2005