Page 1144 - Advanced Organic Chemistry Part B - Reactions & Synthesis

1120 probably two reasons for this: the t-butyl group does not provide any allylic hydrogens
1
and its steric bulk may interfere with approach by O .
2
CHAPTER 12
66
Oxidations
>95
H CH 3 75 CH 3 H H CH 3
(CH ) C CH 3 25 (CH ) C CH 3 (CH 3 3 CH CH 3
) C
3 3
2
3 3
34
Polar functional groups such as carbonyl, cyano, and sulfoxide, as well as silyl
and stannyl groups, exert a strong directing effect, favoring proton removal from the
geminal methyl group. 171
CH 3 X 1 O 2 OOH
CH 3 X
H
H CH 2
CH 3
X = CO CH 3 , CH O, C N,
2
) , Sn(CH )
SOPh, Si(CH 3 3 3 3
Hydroxy 172 and amino 173 groups favor syn stereoselectivity. This is similar to the
substituent effects observed for peroxy acids and suggests that the substituents may
stabilize the TS by hydrogen bonding.
1
Recently techniques have been developed for O oxidations in zeolite cavities. 174
2
1
The photosensitizer is absorbed in the zeolite and generation of O and reaction with
2
the alkene occurs within the cavity. The reactions under these conditions show changes
in both regiochemistry 175 and stereoselectivity. The cis effect is reduced and there is a
preference for hydrogen abstraction from methyl groups.
CH 3 CH 3 O , hν CH 2 CH 3 CH 3 CH 3
2
thionin dye + CH 3
CH 3 CH 3 OOH OOH
zeolite 100 0
CH CN soln 40 60
3
CH 3
CH CH
CH 3 2 3
+ +
O 2 , hν OOH
thionin dye OOH OOH
zeolite 88 2 10
CN soln 40 15 45
CH 3
171 E. L. Clennan, X. Chen, and J. J. Koola, J. Am. Chem. Soc., 112, 5193 (1990); M. Orfanopoulos,
M. Stratakis, and Y. Elemes, J. Am. Chem. Soc., 112, 6417 (1990); W. Adam and M. J. Richter,
Tetrahedron Lett., 34, 8423 (1993).
172 W. Adam and B. Nestler, J. Am. Chem. Soc., 114, 6549 (1992); W. Adam and B. Nestler, J. Am. Chem.
Soc., 115, 5041 (1993); M. Stratakis, M. Orfanopoulos, and C. S. Foote, Tetrahedron Lett., 37, 7159
(1996).
173
H.-G. Brunker and W. Adam, J. Am. Chem. Soc., 117, 3976 (1995).
174 X. Li and V. Ramamurthy, J. Am. Chem. Soc., 118, 10666 (1996).
175
J. Shailaja, J. Sivaguru, R. J. Robbins, V. Ramamurthy, R. B. Sunoj, and J. Chandrasekhar, Tetrahedron,
56, 6927 (2000); E. L. Clennan and J. P. Sram, Tetrahedron, 56, 6945 (2000); M. Stratakis, C. Rabalakos,
G. Mpourmpakis, and L. G. Froudakis, J. Org. Chem., 68, 2839 (2003).