Photochemistry of Substituted Alkyl Phenylglyoxylate
J . Org. Chem., Vol. 62, No. 22, 1997 7831
with argon for 5 min before and during the experiment. The
samples were excited with 355 nm pulses (pulse width ca. 7
ns). Light from a 200 W xenon lamp was focused into the
sample solution and then into a SPEX1680 0.22 mm double
spectrometer. A computer controlled kinetic spectrophotom-
eter (Kinetic Instruments) was used in its absorption mode to
obtain transient spectra and kinetic data. The spectrometer
was interfaced with a digital oscilloscope (Le Croy 9450, 350
MHz bandpass).
3′-Br om op r op yl p h en ylglyoxyla te (1f) (hexanes:ethyl
acetate ) 10:1): Rf in 5/1 (hexanes/ethyl acetate) ) 0.31, yellow
oil, yield 91%. δH (400 MHz) 2.32 (quintet, J ) 6.4 Hz, 2H),
3.51 (t, J ) 6.4 Hz, 2H), 4.54 (t, J ) 6.4 Hz, 2H), 7.50-7.54
(m, 2H), 7.65-7.69 (m, 1H), 7.99-8.02 (m, 2H). δC (APT, 50
MHz) 28.87, 31.14, 63.64, 128.88, 129.92, 132.23, 134.98,
163.49, 185.91. MS 272 (M+ + 2, 0.1), 270 (M+, 0.1), 105 (100),
77 (60). HRMS m/e calculated for C11H11BrO3: 269.9892,
measured: 269.9890.
Gen er a l P r oced u r e for th e DCC Ester ifica tion (syn-
theses of compound 1). To the appropriate hydroxyl com-
pound, benzoylformic acid, and 4-(N,N′-dimethylamino)pyri-
dine (molar ratio: 1.0:1.1:0.1) in a round bottom flask was
added dry dichloromethane to make an approximate 0.2 M
solution. The solution was then placed over ice to cool to 0
°C. An equal molar amount of 1,3-dicyclohexylcarbodiimide
(DCC) in dry dichloromethane was added dropwise to the
stirred solution. Usually, a white precipitate formed instantly.
The mixture was then allow to warm up to room temperature
and stirred overnight. The precipitate was filtered and the
solvent evaporated in vacuo. Purification by flash column
chromatography with indicated eluents following the com-
pound name produces 1 in good yields.
2′-Ch lor oet h yl p h en ylglyoxyla t e (1a ) (hexanes:ethyl
acetate ) 10:1): Rf in 5/1 (hexanes/ethyl acetate) ) 0.32,
yellowish oil, yield 90%. δH (400 MHz) 3.80-3.83 (m, 2H),
4.63-4.65 (m, 2H), 7.49-7.53 (m, 2H), 7.64-7.68 (m, 1H),
8.01-8.04 (m, 2H). δC (APT, 50 MHz) 40.93, 65.21, 128.84,
129.94, 132.03, 135.03, 163.13, 185.58. MS 214 (M+ + 2, 0.05),
212 (M+, 0.1), 105 (100), 77 (48), 51 (21). HRMS m/e calculated
for C10H9ClO3: 212.0240, measured: 212.0241.
3′-(P h en ylth io)p r op yl P h en ylglyoxyla te (1g). 3-(Phe-
nylthio)-1-propanol was synthesized by a general method
described previously.18b δH (400 MHz) 1.76 (quintet, J ) 6.4
Hz, 2H), 2.31 (s, 1H), 2.91 (t, J ) 6.4 Hz, 2H), 3.62 (t, J ) 6.4
Hz, 2H), 7.05-7.09 (m, 1H), 7.16-7.20 (m, 2H), 7.23-7.25 (m,
2H). δC (APT, 50 MHz) 29.96, 31.51, 61.01, 125.81, 128.77,
128.94, 136.10. MS 168 (M+, 44), 123 (12), 110 (100). HRMS
m/e calculated for C9H12SO: 168.0609, measured: 168.0609.
Compound 1g: (hexanes:ethyl acetate ) 10:1), Rf in 5/1
(hexanes/ethyl acetate) ) 0.40, yellow oil, yield 87%. δH (400
MHz) 2.08 (quintet, J ) 6.4 Hz, 2H), 3.03 (t, J ) 6.4 Hz, 2H),
4.50 (t, J ) 6.4 Hz, 2H), 7.15-7.20 (m, 1H), 7.25-7.29 (m, 2H),
7.33-7.36 (m, 2H), 7.47-7.51 (m, 2H), 7.62-7.66 (m, 1H),
7.98-8.00 (m, 2H). δC (APT, 50 MHz) 27.85, 29.91, 64.30,
126.26, 128.84, 128.95, 129.52, 129.94, 132.27, 134.90, 135.40,
163.60, 186.04. MS 300 (M+, 4.6), 149 (19), 123 (8.5), 105 (100),
77 (25). HRMS m/e calculated for C17H16SO3: 300.0820,
measured: 300.0820.
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 benzene and
sealed with
a rubber septum bound by sticky parafilm.
2′-Br om oeth yl p h en ylglyoxyla te (1b) (hexanes:ethyl ac-
etate ) 10:1): Rf in 5/1 (hexanes/ethyl acetate) ) 0.30, yellow
oil, yield 86%. δH (400 MHz) 3.64 (t, J ) 6.2 Hz, 2H), 4.70 (t,
J ) 6.2 Hz, 2H), 7.49-7.54 (m, 2H), 7.64-7.69 (m, 1H), 8.01-
8.04 (m, 2H). δC (APT, 50 MHz) 27.70, 64.99, 128.83, 129.94,
132.01, 135.01, 162.96, 185.51. MS (EI): 258 (M+ + 2, 0.08),
256 (M+, 0.07), 105 (100), 77 (57), 51 (26). MS (CI): 259 (M +
Degassing was achieved by bubbling dry argon gas through
the solution for 10-15 min. Irradiation was carried out in a
Rayonet RPR-100 photoreactor equipped with sixteen 350 nm
GE F8T5‚BLB UV lamps. After irradiation, the solvent was
evaporated on a rotary evaporator, and the resulting mixture
was chromatographed under pressure.
2 + 1), 257 (M + 1). HRMS (CI) m/e calculated for C10H10
BrO3 (M + 1): 256.9813, measured: 256.9822.
-
Vin yl p h en ylglyoxyla te (2) was isolated in a photosylate
of 1d (hexanes:ethyl acetate ) 10:1): Rf in 5/1 (hexanes/ethyl
acetate) ) 0.46, yellow oil, yield 54%. δH (400 MHz) 4.85 (dd,
J 1 ) 6.4 Hz, J 2 ) 2.4 Hz, 1H), 5.16 (dd, J 1 ) 13.6 Hz, J 2 ) 2.4
Hz, 1H), 7.44 (dd, J 1 ) 13.6 Hz, J 2 ) 6.4 Hz, 1H), 7.50-7.54
(m, 2H), 7.65-7.69 (m, 1H), 8.03-8.06 (m, 2H). δC (APT, 50
MHz) 100.93, 128.90, 130.05, 132.08, 135.14, 140.18, 160.02,
184.58. MS (EI): 148 (M+ - 28, 0.8), 105 (100), 77 (60), 51
(27). MS (CI): 177 (M + 1). HRMS (CI) m/e calculated for
C10H9O3 (M + 1): 177.0552, measured: 177.0550. Its struc-
ture was confirmed by independent synthesis.12
2′-Iod oeth yl p h en ylglyoxyla te (1c) (hexanes:ethyl ac-
etate ) 10:1): Rf in 5/1 (hexanes/ethyl acetate) ) 0.30, yellow
oil, yield 85%. δH (400 MHz) 3.42 (t, J ) 7.0 Hz, 2H), 4.65 (t,
J ) 7.0 Hz, 2H), 7.51-7.54 (m, 2H), 7.65-7.70 (m, 1H), 8.02-
8.05 (m, 2H). δC (APT, 50 MHz) -1.21, 65.90, 128.86, 130.03,
132.07, 135.05, 162.80, 185.53. MS (EI) 304 (M+, 0.09), 155
(14), 105 (100), 77 (41), 51 (20). MS (CI): 305 (M + 1). HRMS
(CI) m/e calculated for C10H10IO3 (M + 1): 304.9675, mea-
sured: 304.9677.
2′-(P h en ylth io)eth yl p h en ylglyoxyla te (1d ) (hexanes:
ethyl acetate ) 10:1): Rf in 5/1 (hexanes/ethyl acetate) ) 0.38,
yellow oil, yield 81%. δH (400 MHz) 3.25 (t, J ) 7.0 Hz, 2H),
4.51 (t, J ) 7.0 Hz, 2H), 7.18-7.23 (m, 1H), 7.26-7.31 (m, 2H),
7.40-7.43 (m, 2H), 7.46-7.51 (m, 2H), 7.61-7.66 (m, 1H),
7.99-8.02 (m, 2H). δC (APT, 50 MHz) 32.13, 64.08, 126.88,
128.79, 129.06, 129.97, 130.21, 132.16, 134.25, 134.92, 163.27,
185.75. MS 286 (M+, 4.6), 136 (24), 105 (100), 77 (53), 51 (21).
HRMS m/e calculated for C16H14SO3: 286.0664, measured:
286.0663.
2′-(P h en ylsu lfin yl)eth yl p h en ylglyoxyla te (1e) (hex-
anes:ethyl acetate ) 1:1): Rf in ethyl acetate ) 0.56, yellow
oil, yield 75% (two steps). δH (400 MHz) 3.16 (dt, J 1 ) 5.6 Hz,
J 2 ) 14 Hz, 1H), 3.24-3.31 (m, 1H), 4.65 (dt, J 1 ) 5.6 Hz, J 2
) 12 Hz, 1H), 4.80-4.86 (m, 1H), 7.47-7.54 (m, 5H), 7.64-
7.69 (m, 3H), 7.99-8.01 (m, 2H). δC (APT, 50 MHz) 55.18,
58.58, 123.66, 128.81, 129.32, 129.92, 131.25, 131.96, 135.03,
142.78, 162.89, 185.22. MS (EI): 302 (M+, 0.2), 177 (34), 105
(100), 77 (84), 51 (38). MS (CI): 303 (M + 1). HRMS (CI) m/e
calculated for C16H15SO4 (M + 1): 303.0691, measured:
303.0684.
Ack n ow led gm en t. We thank the National Science
Foundation (DMR-9526755) and the Office of Naval
Research (Navy N00014-91-J -1921) for financial support
of this work. Conversations with Dr. G. S. Hammond
are gratefully acknowledged. We thank Dr. M. A. J .
Rodgers for making the laser flash photolysis facilities
available to us.
Su p p or tin g In for m a tion Ava ila ble: 1H and 13C NMR
1
spectra for the new compounds 1a -g, 2, and HNMR spectra
used to quantify 2/5 in the reactions of 1b and 1d (20 pages).
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