Figure 2. Consumption of (a) 1a, (b) 1b, (c) 1c, and yield of
photoproducts using different cutoff filters.8,9 Symbols: aryl pentyl
telluride (1a-c, 9), pentanal (2, b), 1-pentene (3, 2), and pentanol
(4, (). Concentration of 1a-c ) 1 mM in hexane, light source )
500 W xenon short-arc lamp fitted with an 18 cm water filter (17.5
mW·cm-2) and a cutoff filter, irradiation time ) 1 min, reaction
vessel ) quartz cell (optical path ) 10 mm), oxygen atm, rt.
Wavelength of light, UV-29 ) >290 nm; UV-31 ) >310 nm; UV-
33 ) >330 nm; UV-35 ) >350 nm; UV-37 ) >370 nm.
Figure 1. Absorption spectra of n-pentyl phenyl telluride (1a, solid
line), 2-naphthyl n-pentyl telluride (1b, broken line), and 1-naphthyl
n-pentyl telluride (1c, dotted line). Concentration ) 10-5 M in
n-hexane, optical path ) 10 mm.
Figure 2 shows the results of the effect of wavelength and
aryl group on the photolysis. The photolyses were conducted
in hexane under an oxygen atmosphere with a xenon lamp
fitted with different cutoff filters; the photoproducts were
assigned and quantified by GC analyses in comparison with
authentic samples.8 Figure 2 shows that the consumption of
1a-c decreased with increased wavelength of the irradiated
light, which can be explained by a decrease in the absorption
of light (cf. Figure 1). In contrast, the yield of 2 showed a
small maximum when a UV-33 filter was used, where the
yield did not depend on the structure of the aryl group. These
results indicated that irradiation using a UV-33 filter was
the optimal condition to obtain the best balance between the
rate of photolysis and the yield of product.
compared with that of the C-Se bonds.11 Besides products
2-4 that were generated from pentyl moiety, ArH, ArOH,
and ArTeTeAr were formed from aryl moieties with the total
yield of 75-85%.8 For comparison, photolyses of 1- and
2-naphthyl pentyl sulfides were conducted;8 however, the
rate of the reaction was more than 50-fold slower and the
yield of 2 was less than 20%.
The effect of irradiation time was investigated using a
xenon lamp with a UV-33 filter (Figure 3). For tellurides
1a-c, the reaction was complete within 2 min with a similar
yield of 2. The rate of photolysis was more than 10-fold
faster than the selenium analogue,10 which was most prob-
ably due to the smaller bond energy of the C-Te bonds
Figure 3. Consumption of (a) 1a, (b) 1b, (c) 1c, and yield of
photoproducts as a function of irradiation time.9 Symbols: aryl
pentyl telluride (1a-c, 9), pentanal (2, b), 1-pentene (3, 2), and
pentanol (4, (). Concentration of 1a-c ) 1 mM in hexane, light
source ) 500 W xenon short-arc lamp fitted with an 18 cm water
filter and a UV-33 filter (14.7 mW·cm-2), reaction vessel ) quartz
cell (optical path ) 10 mm), oxygen atm, rt.
(4) (a) Spencer, H. K.; Cava, M. P. J. Org. Chem. 1977, 42, 2937. (b)
Browm, D. H.; Cross, R. J.; Millington, D. J. Organomet. Chem. 1977,
125, 219. (c) Barton, D. H. R.; Ozbalik, N.; Sarma, J. C. Tetrahedron Lett.
1988, 29, 6581. (d) Barton, D. H. R.; Ramesh, M. J. Am. Chem. Soc. 1990,
112, 891. (e) Barton, D. H. R.; Dalko, P. I.; Gero, S. D. Tetrahedron Lett.
1991, 32, 4713. (f) Barton, D. H. R.; Camara, J.; Cheng, X.; Gero, S. D.;
Jaszberenyi, J. C.; Quiclet-Sire, B. Tetrahedron 1992, 48, 9261. (g) Bell,
W.; Cole-Hamilton, D. J.; Culshaw, P. N.; McQueen, A. E. D.; Shenai-
Khatkhate, D. V.; Walton, J. C. J. Organomet. Chem. 1992, 430, 43. (h)
Engman, L.; Gupta, V. J. Chem. Soc., Chem. Commun. 1995, 2515. (i)
Barton, D. H. R.; Gero, S. D.; Holliday, P.; Quiclet-Sire, B. Tetrahedron
1996, 52, 8233. (j) He, W.; Togo, H.; Ogawa, H.; Yokoyama, M. Heteroat.
Chem. 1997, 8, 411. (k) Engman, L.; Gupta, V. J. Org. Chem. 1997, 62,
157.
In analogy with the reaction mechanism of pentyl phenyl
selenide,10,12 products 2-4 were expected to be formed via
carbon radicals that were generated by photochemical
alkyl-Te bond cleavage.5 The pentyl group was quantita-
tively transformed to products 2-4, which was confirmed
by the sum of the three products equaling 100%. The yield
of 2 was not affected by the difference in the aryl group but
showed a slight difference in the rate of the reaction and the
(5) (a) Yamago, S.; Hashidume, M.; Yoshida, J. Chem. Lett. 2000, 1234.
(b) Pola, J.; Ouchi, A. J. Organomet. Chem. 2001, 629, 93. (c) Pola, J.;
Bastl, Z.; Subrt, J.; Ouchi, A. Appl. Organomet. Chem. 2001, 15, 924. (d)
Yamago, S.; Iida, K.; Yoshida, J. Tetrahedron Lett. 2001, 42, 5061. (e)
Yamago, S.; Hashidume, M.; Yoshida, J. Tetrahedron 2002, 58, 6805, and
references cited therein.
(6) Mason, W. R. J. Phys. Chem. 1996, 100, 8139.
(7) Yamago, S.; Ukai, Y.; Matsumoto, A.; Nakamura, Y. J. Am. Chem.
Soc. 2009, 131, 2100.
(8) Original data and/or experimental details are given as Supporting
Information.
(11) Batt, L. In the Chemistry of Organic Selenium and Tellurium
Compounds; Patai, S., Rappoport, Z., Eds.; Wiley: Chichester, UK, 1986;
Vol. 1, pp 158-160, Chapter 4.
(9) Yields of the products are based on the consumed starting material.
The results are the average of at least two independent runs.
(10) Hyugano, T.; Liu, S.; Ouchi, A. J. Org. Chem. 2008, 73, 8861.
(12) Ouchi, A.; Liu, S.; Li, Z.; Kumar, S. A.; Suzuki, T.; Hyugano, T.;
Kitahara, H. J. Org. Chem. 2007, 72, 8700
.
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