4344
D. S. Kim et al. / Tetrahedron Letters 42 (2001) 4341–4344
Finally, we wish to emphasize that the enhancement of
de was accomplished in this study not through the
modification or functionalization of substrate but by
optimizing the sensitizer structure and spin-state as well
as the other external factors. This methodology, unique
to photochemistry, should be quite useful and generally
applicable, and inherently poor de’s obtained upon
direct irradiation of enantiomeric substrates can be
improved by employing a proper sensitizer that governs
the stereochemical outcome of asymmetric photoreac-
tion through the excited-state interactions. Further
investigation of the detailed mechanism and applica-
tions of this methodology to other systems are currently
in progress.
Perkin. Trans. 2 1980, 1672; (c) Takamuku, S.; Sakurai,
H.; Inoue, Y.; Kunitomi, Y. J. Chem. Soc., Perkin. Trans.
2 1980, 1687; (d) Inoue, Y.; Yokoyama, T.; Yamasaki, N.;
Tai, A. J. Am. Chem. Soc. 1989, 111, 6480; (e) Inoue, Y.;
Shimoyama, H.; Yamasaki, N.; Tai, A. Chem. Lett. 1991,
539; (f) Inoue, Y.; Yamasaki, N.; Yokoyama, T.; Tai, A.
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Inoue, Y.; Matsushima, E.; Wada, T. J. Am. Chem. Soc.
1998, 120, 10687; (k) Hoffmann, R.; Inoue, Y. J. Am.
Chem. Soc. 1999, 121, 10702.
5. (a) Kropp, P. J. J. Am. Chem. Soc. 1966, 88, 4092; (b)
Kropp, P. J.; Krauss, H. J. J. Am. Chem. Soc. 1967, 89,
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6. From the Eyring equation, ln[(100+% de)/(100−% de)]=−
DDH‡/RT+DDS‡/R, the product de was governed not only
by the enthalpy of activation (DDH‡) but also by the
entropy of activation (DDS‡).
Acknowledgements
This work was supported by the Center for Molecular
Design and Synthesis-KOSEF and School of Molecular
Science-BK21.
7. Buschmann, H.; Scharf, H.-D.; Hoffmann, N.; Plath, M.
W.; Runsink, J. J. Am. Chem. Soc. 1989, 111, 5367.
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9. Compound 2: 1H NMR (400 MHz, CDCl3, 25°C, TMS): l
4.66 (s, 2H), 4.59 (s, 2H), 2.31 (t, J=6 Hz, 1H), 2.03 (m,
4H), 1.69 (s, 3H), 1.29–1.23 (m, 4H); 13C NMR (CDCl3,
100 MHz): l 150.1, 149.3, 108.4, 106.9, 45.0, 34.8, 33.0,
20.8; HRMS (M+) calcd for C10H16: 136.1252. Found:
136.1252. Compound 3: 1H NMR (400 MHz, CDCl3,
25°C, TMS): l 4.66 (s, 2H), 3.21 (s, 3H), 1.86 (t, J=12 Hz,
1H), 1.74 (s, 2H), 1.70 (s, 2H), 1.69 (s, 3H), 1.45 (t, J=15
Hz, 2H), 1.31 (t, J=15 Hz, 2H), 1.16 (s, 3H); 13C NMR
(CDCl3, 100 MHz): l 149.7, 108.4, 74.5, 48.4, 44.6, 36.2,
28.4, 21.1, 20.5; HRMS (M+) calcd for C11H20O: 168.1514.
Found: 168.1554. Compound 4: 1H NMR (400 MHz,
CDCl3, 25°C, TMS): l 4.66 (s, 2H), 3.19 (s, 3H), 1.86 (t,
J=12 Hz, 1H), 1.74 (s, 2H), 1.70 (s, 2H), 1.69 (s, 3H), 1.45
(t, J=15 Hz, 2H), 1.31 (t, J=15 Hz, 2H), 1.16 (s, 3H); 13C
NMR (CDCl3, 100 MHz): l 149.7, 108.4, 74.5, 48.4, 44.6,
36.2, 28.4, 21.1, 20.5; HRMS (M+) calcd for C11H20O:
168.1514. Found: 168.1554.
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Chem. Soc., Chem. Commun. 1978, 1024; (b) Inoue, Y.;
Takamuku, S.; Kunitomi, Y.; Sakurai, H. J. Chem. Soc.,
.