Photochemistry of Alkenyl Phenylglyoxylates
J . Org. Chem., Vol. 62, No. 20, 1997 6825
eter or a Varian Unity Plus 400 NMR spectrometer using
chloroform-d as solvent. Chemical shifts are in ppm with TMS
as the internal standard. GC measurements were carried out
on a Hewlett-Packard (HP) 5890 gas chromatograph with a
30 m × 0.253 mm i.d. × 0.25 µm film thickness DB-1 column
(J & B Scientific) and a flame ionization detector. GC/MS were
taken on a Hewlett-Packard 5988 mass spectrometer coupled
to a HP 5880A GC with a 30 m × 0.25 mm i.d. × 0.25 µm film
thickness DB-5 ms column (J & B Scientific), interfaced to a
HP 2623A data processor. Infrared spectra were taken with
a Galaxy series 6020 FTIR spectrometer. Thin layer chroma-
tography was performed with Whatman silica gel-coated TLC
plates. Silica gel (60 Å, 60-200 mesh) used in column
chromatography was from J . T. Baker Chemical Co. Cyclic
voltammograms were recorded on an BAS 100A electrochemi-
cal analyzer with platinum as both the working and counter
electrodes and Ag/AgCl as the reference electrode. The redox
potentials obtained were corrected to vs standard calomel
electrode (SCE) by measuring ferrocenium/ferrocene reference
(+0.425 V in acetonitrile vs SCE)29 at identical conditions. The
solutions were purged with argon when necessary. High-
resolution mass spectra were obtained from the University of
Illinois at Urbana-Champaign.
Qu a n tu m Yield s. A benzene solution (0.1 M) of valero-
phenone as actinometer (Φacetophenone ) 0.33)30 was always
irradiated parallel to the sample solution on a “merry-go-
round”. The disappearance of starting alkenyl phenylgly-
oxylate was monitored by NMR since dimers resulting from
hydrogen abstractions decompose in the GC. The signals from
the aromatic hydrogens of the reaction mixture were used as
the internal standard since the total number of such hydrogens
are conserved in the reaction process. The disappearance of
starting alkenyl phenylglyoxylate was monitored by its dis-
tinctive downfield (≈8.00 ppm) aromatic hydrogen signals. The
appearance of acetophenone in the actinometer and of products
9-11 was conveniently monitored by GC. The GC was
calibrated against these compounds using chlorobenzene as
the internal standard. Quantum yields reported are averages
of three measurements.
(m, 1H), 5.73-5.79 (m, 1H), 7.48-7.52 (m, 2H), 7.63-7.67 (m,
1H), 7.98-8.01 (m, 2H); 13C NMR (50 MHz) δ 13.57, 22.41,
29.51, 61.77, 122.00, 128.79, 129.92, 132.39, 134.81, 136.91,
163.67, 186.20; MS 41 (11), 55 (15), 77 (34), 83 (18), 105 (100),
123 (1.8), 151 (0.1), 205 (0.1); IR (film) 2963.57, 2870.96,
1736.47, 1690.16, 1597.55, 1196.23, 910.68; HRMS m/z calcd
for C14H16O3 232.1099, found 232.1096.
tr a n s-2′-Hexen yl p h en ylglyoxyla te (tr a n s-2): hexanes:
ethyl acetate ) 15:1; 1H NMR (400 MHz) δ 0.91 (t, J ) 7.2
Hz, 3H), 1.43 (sexet, J ) 7.2 Hz, 2H), 2.06 (q, J ) 7.2 Hz, 2H),
4.83 (dq, J 1 ) 6.4 Hz, J 2 ) 1.2 Hz, 2H), 5.67 (dtt, J 1 ) 15.6
Hz, J 2 ) 6.4 Hz, J 3 ) 1.6 Hz, 1H), 5.91 (dtt, J 1 ) 15.6 Hz, J 2
) 6.4 Hz, J 3 ) 1.2 Hz, 1H), 7.48-7.52 (m, 2H), 7.63-7.67 (m,
1H), 7.99-8.02 (m, 2H); 13C NMR (50 MHz) δ 13.53, 21.84,
34.22, 66.83, 122.53, 128.79, 129.95, 132.39, 134.81, 138.42,
163.58, 186.24; MS 41 (14), 55 (22), 77 (38), 83 (26), 105 (100),
122 (0.3); IR (film) 2963.57, 2874.82, 1736.47, 1690.16, 1597.55,
1196.23, 910.68; HRMS m/z calcd for C14H16O3 232.1099, found
232.1096.
3′-Met h ylb u t -2′-en yl p h en ylglyoxyla t e (3): hexanes:
1
ethyl acetate ) 15:1; H NMR (400 MHz) δ 1.78 (d, J ) 1.2
Hz, 3H), 1.79 (d, J ) 1.2 Hz, 3H), 4.88 (d, J ) 7.6 Hz, 2H),
5.47 (tq, J 1 ) 7.6 Hz, J 2 ) 1.2 Hz, 1H), 7.48-7.52 (m, 2H),
7.63-7.67 (m, 1H), 7.99-8.01 (m, 2H); 13C NMR (50 MHz) δ
18.08, 25.74, 62.90, 117.25, 128.79, 129.94, 132.45, 134.76,
141.07, 163.80, 186.35; MS 41 (45), 57 (19), 69 (99), 77 (52),
105 (100); HRMS m/z calcd for C13H14O3 218.0943, found
218.0942.
cis-3′-Hexen yl p h en ylglyoxyla te (cis-4): hexanes:ethyl
acetate ) 15:1; 1H NMR (400 MHz) δ 0.95 (t, J ) 7.6 Hz, 3H),
2.07 (quintet of triplets, J 1 ) 7.6 Hz, J 2 ) 1.2 Hz, 2H), 2.55
(qt, J 1 ) 7.6 Hz, J 2 ) 1.2 Hz, 2H), 4.39 (t, J ) 7.6 Hz, 2H),
5.36 (dtt, J 1 ) 10.8 Hz, J 2 ) 7.6 Hz, J 3 ) 1.2 Hz, 1H), 5.55
(dtt, J 1 ) 10.8 Hz, J 2 ) 7.6 Hz, J 3 ) 1.2 Hz, 1H), 7.27-7.53
(m, 2H), 7.64-7.68 (m, 1H), 7.99-8.02 (m, 2H); 13C NMR (50
MHz) δ 14.09, 20.59, 26.56, 65.55, 122.78, 128.81, 132.37,
134.85, 135.30, 163.78, 186.29; MS 41 (6.9), 55 (11), 67 (8.5),
77 (29), 82 (34), 105 (100), 152 (0.1), 187 (0.1); HRMS m/z calcd
for C14H16O3 232.1099, found 232.1096.
tr a n s-3′-Hexen yl p h en ylglyoxyla te (tr a n s-4): hexanes:
ethyl acetate ) 15:1; 1H NMR (400 MHz) δ 0.97 (t, J ) 7.6
Hz, 3H), 2.02 (quintet of triplets, J 1 ) 7.6 Hz, J 2 ) 1.2 Hz,
2H), 2.48 (qt, J 1 ) 7.6 Hz, J 2 ) 1.2 Hz, 2H), 4.40 (t, J ) 7.6
Hz, 2H), 5.41 (dtt, J 1 ) 15.0 Hz, J 2 ) 7.6 Hz, J 3 ) 1.2 Hz,
1H), 5.62 (dtt, J 1 ) 15.0 Hz, J 2 ) 7.6 Hz, J 3 ) 1.2 Hz, 1H),
Tim e-Resolved La ser F la sh P h otolysis. Nanosecond
laser flash photolysis was carried out on a setup described by
Ford and Rodgers31 using the third harmonic of a Q-switched
Nd:YAG laser (Continuum, YG660) as excitation source. The
sample solution in a quartz cuvette was purged with argon
for 5 min before and during the experiment. The samples were
excited with 355 nm pulses (pulse width ca. 7 ns).
7.27-7.53 (m, 2H), 7.64-7.68 (m, 1H), 7.99-8.02 (m, 2H); 13
C
NMR (50 MHz) δ 13.47, 25.48, 31.71, 65.65, 123.17, 128.75,
129.90, 132.34, 134.76, 135.74, 163.76, 186.31; MS 41 (6.3),
55 (10), 77 (27), 82 (31), 105 (100), 127 (0.3), 152 (0.1), 187
(0.1); IR (film) 2967.53, 2878.67, 1736.47, 1690.16, 1597.55,
1200.09, 910.68; HRMS m/z calcd for C14H16O3 232.1099, found
232.1099.
Allyl P h en ylglyoxyla te (1). After passing through dry
HCl (generated in situ by adding concentrated H2SO4 to NaCl)
for 2 h, 20 mL of allyl alcohol was added to 1.5 g (10 mmol) of
benzoylformic acid, and the mixture was refluxed for 2 h. The
resulting solution was extracted three times with dichloro-
methane, and the combined organic layers were washed with
saturated NaHCO3 solution and water each three times and
dried over anhydrous MgSO4. Evaporating solvent under
vacuum left 1.5 g of the title compound as a slightly yellowish
oil: yield 85%; 1H NMR (400 MHz) δ 4.88 (dt, J 1 ) 6, 1.2 Hz,
2H), 5.35 (dq, J 1 ) 10.4, 2.4 Hz, 1H), 5.46 (dq, J 1 ) 17.2, 1.2
Hz, 1H), 5.98-6.07 (m, 2H), 7.50-7.54 (m, 2H), 7.64-7.68 (m,
1H), 8.00-8.02 (m, 2H); 13C NMR (50 MHz) δ 66.57, 120.02,
128.90, 130.03, 130.74, 132.39, 134.94, 163.42, 186.04; MS 51
(12), 77 (39), 105 (100), 162 (0.2), 190 (0.3); HRMS m/z calcd
for C11H10O3 190.0630, found 190.0629.
Gen er a l P r oced u r e for DCC Ester ifica tion (Syn th esis
of com p ou n d s 2-7). Similar procedures to that described
earlier9 produced these R-keto esters in yields better than 85%.
cis-2′-Hexen yl p h en ylglyoxyla te (cis-2): hexanes:ethyl
acetate ) 15:1; 1H NMR (400 MHz) δ 0.93 (t, J ) 7.2 Hz, 3H),
1.43 (sexet, J ) 7.2 Hz, 2H), 2.15 (qd, J 1 ) 7.2 Hz, J 2 ) 1.2
Hz, 2H), 4.94 (dd, J 1 ) 6.8 Hz, J 2 ) 0.8 Hz, 2H), 5.63-5.70
4′-Met h ylp en t -3′-en yl p h en ylglyoxyla t e (5): hexanes:
1
ethyl acetate ) 15:1; H NMR (400 MHz) δ 1.64 (s, 3H), 1.72
(d, J ) 1.2 Hz, 3H), 2.48 (qt, J 1 ) 7.2 Hz, J 2 ) 1.2 Hz, 2H),
4.37 (t, J ) 7.2 Hz, 2H), 5.15 (triplet of quintets, J 1 ) 7.2 Hz,
J 2 ) 1.2 Hz, 1H), 7.49-7.53 (m, 2H), 7.63-7.67 (m, 1H), 7.99-
8.01 (m, 2H); 13C NMR (50 MHz) δ 17.77, 25.68, 27.47, 65.70,
118.45, 128.81, 129.95, 132.41, 134.81, 135.45, 163.86, 186.40;
MS 41 (11), 55 (19), 67 (14), 77 (32), 82 (58), 105 (100), 187
(0.2), 232 (0.4); HRMS m/z calcd for C14H16O3 232.1099, found
232.1099.
1′,5′-Dim eth ylh ex-4′-en yl p h en ylglyoxyla te (6): hex-
1
anes:ethyl acetate ) 15:1; H NMR (400 MHz) δ 1.40 (d, J )
6.0 Hz, 3H), 1.60 (d, J ) 0.4 Hz, 3H), 1.69 (d, J ) 1.2 Hz, 3H),
1.79 (q, J ) 7.2 Hz, 1H), 1.83 (t, J ) 6.4 Hz, 1H), 2.09 (q, J )
7.2 Hz, 2H), 5.11 (triplet of quintets, J 1 ) 7.2 Hz, J 2 ) 1.2 Hz,
2H), 5.18-5.26 (m, 1H), 7.49-7.53 (m, 2H), 7.63-7.67 (m, 1H),
7.98-8.01 (m, 2H); 13C NMR (50 MHz) δ 17.52, 19.86, 23.88,
25.63, 35.73, 73.58, 122.91, 128.84, 129.90, 132.61, 134.76,
163.78, 186.69; MS 41 (30), 55 (16), 69 (92), 77 (41), 95 (46),
105 (100), 110 (69), 155 (2.5); HRMS m/z calcd for C16H20O3
260.1412, found 260.1412.
(29) Meites, L.; Zuman, P. CRC Handbook Series in Organic
Electrochemistry; CRC Press: Boca Raton, FL.
(30) Lewis, F. D.; Hilliard, T. A. J . Am. Chem. Soc. 1972, 94, 3852-
3857.
(31) Ford, W. E.; Rodgers, M. A. J . J . Phys. Chem. 1994,98, 3822-
3831.
Gen er a l P r oced u r es for Ir r a d ia tion of Sa m p les a n d
Isola tin g P r od u cts. Samples were dissolved in the proper
solvent and sealed with a rubber septum bound by sticky