Page 1114 - Advanced Organic Chemistry Part B - Reactions & Synthesis

1090

CHAPTER 12
N N N N N N
Oxidations
Mn V Mn VI Mn III
– O O – O – O O – O – O – O
O
RCH CHR RCH CHR RCH CHR

Scheme 12.10 gives some examples of these oxidations. Entry 1 is one of several
aryl-conjugated alkenes that were successfully epoxidized. Entry 2 is a reaction that
was applied to enantioselective synthesis of the taxol side chain. Entry 3 demonstrates

Scheme 12.10. Enantioselective Epoxidation with Chiral Manganese Catalysts a

1 b CH O CH 3
O 3 2 mol % catalyst E

CH
CH 3 3
NaOCl 72% yield,
O 98% e.e.
C H
2 c 6 mol % catalyst E, Ph CO 2 2 5
4-phenylpyridine-N-oxide
Z-PhCH CHCO 2 2 5
C H
O 56% yield,
NaOCl
95–97% e.e.
3 d
3 mol % catalyst E,
C H O C C H O C
2
2 5
NaOCl 2 5 2
O
81% yield,
87% e.e.
4 e OCH
OCH 3 1 mol % catalyst E, 3
O 0.4 mol % 4-(3-phenylpropyl)- O
pyridine-N-oxide
N N
NaOCl O
Ph
Ph 58% yield,
H H 89% e.e.
5 f
O
5 mol % catalyst E,
NCO C(CH ) m-CPBA, 2 equiv
2
3 3
C(CH )
NCO 2 3 3
MMNO, 5 equiv
OCH Ph 70% yield,
2
OCH Ph 92% e.e.
2
a. The structure of catalyst E is shown on p. 1088.
b. E. N. Jacobsen, W. Zhang, A. R. Muci, J. R. Ecker, and L. Deng, J. Am. Chem. Soc., 113, 7063 (1991).
c. L. Deng and E. N. Jacobsen, J. Org. Chem., 57, 4320 (1992).
d. S. Chang, N. H. Lee, and E. N. Jacobsen, J. Org. Chem., 58, 6939 (1993).
e. J. E. Lynch, W.-B. Choi, H. R. O. Churchill, R. P. Volante, R. A. Reamer, and R. G. Ball, J. Org. Chem., 62,
9223 (1997).
f. D. L. Boger, J. A. McKie, and C. W. Boyce, Synlett, 515 (1997).