Page 1146 - Advanced Organic Chemistry Part B - Reactions & Synthesis

1122 +
O +
+
+
CHAPTER 12 O O
2.38 Å
Oxidations O
2.15 Å
H C CH 3
3
H H CH
H C 3
3
H 3 C CH 3
Fig. 12.13. Perepoxide transition structures from Z-2-butene and
2,3-dimethyl-2-butene. Reproduced from J. Am. Chem. Soc., 125,
1319 (2003), by permission of the American Chemical Society.

1
can serve as a O source. The reactions in Entries 3 and 4 are representative photo-
2
sensitized procedures with subsequent reduction of the hydroperoxide. Entry 5 used
tetra-(perfluorophenyl)phorphyrin as the photosensitizer. This compound, as well as
the tetra-(2,6-dichlorophenyl) analog, is reported to have improved stability to degra-
dation under the reaction conditions. In this case the intermediate hydroperoxide was
dehydrated to an enone using acetic anhydride. This reaction was carried out on a
25-g scale.
Certain compounds react with singlet oxygen in a different manner, giving dioxe-
tanes as products. 178

R R O O
1
+ O 2 R R
R R R R

This reaction is not usually a major factor with alkenes bearing only alkyl groups,
but is important for vinyl ethers and other alkenes with donor substituents. These

2.14
O 2 2.07 O 2 O 1
O 1 1.72 1.85
2.20 H
1.11 H H CH 3
H CH 2 1.15 2.25
H C
2
H
H 3 C 1.11 CH 3
CH 2
Fig. 12.14. Competing cis abstraction and trans abstraction transition structures
for hydroperoxide formation 2-methyl-2-butene. Adapted J. Am. Chem. Soc., 125,
1319 (2003), by permission of the American Chemical Society.

178
W. Fenical, D. R. Kearns, and P. Radlick, J. Am. Chem. Soc., 91, 3396 (1969); S. Mazur and C. S. Foote,
J. Am. Chem. Soc., 92, 3225 (1970); P. D. Bartlett and A. P. Schaap, J. Am. Chem. Soc., 92, 3223 (1970).