Page 1141 - Advanced Organic Chemistry Part B - Reactions & Synthesis

In many allylic oxidations, the double bond is found in a position indicating that an 1117
allylic transposition occurs during the oxidation.
SECTION 12.3
CH 3 CH 3 Allylic Oxidation
CrO –pyridine
3
Cl
CH 2 2 O 68% Ref. 156
Detailed mechanistic understanding of the allylic oxidation has not been developed.
One possibility is that an intermediate oxidation state of Cr, specifically Cr(IV), acts
as the key reagent by abstracting hydrogen. 160
Several catalytic systems based on copper can also achieve allylic oxidation. These
reactions involve induced decomposition of peroxy esters (see Part A, Section 11.1.4).
When chiral copper ligands are used, enantioselectivity can be achieved. Table 12.1
shows some results for the oxidation of cyclohexene under these conditions.

12.3.2. Reaction of Alkenes with Singlet Oxygen

Among the oxidants that add oxygen at carbon-carbon double bonds is singlet
oxygen. 161 For most alkenes this reaction proceeds with the removal of an allylic

Table 12.1. Enantioselective Copper-Catalyzed Allylic Oxidation of Cyclohexene
Catalyst Yield% e.e.%
CH 3 CH 3
O O
1 a N N 43 80
C(CH )
(CH ) C 3 3
3 3

Ph O O Ph
2 b 73 75
Ph N N Ph
) C C(CH )
(CH 3 3 3 3
O
3 c ( ) CH 19 42
3
N
Ph
CO H
2
4 d 67 50
NH
a. M. B. Andrus and X. Chen, Tetrahedron, 53, 16229 (1997).
b. G. Sekar, A. Datta Gupta, and V. K. Singh, J. Org. Chem., 62, 2961 (1998).
c. K. Kawasaki and T. Katsuki, Tetrahedron, 53, 6337 (1997).
d. M. J. Sodergren and P. G. Andersson, Tetrahedron Lett., 37, 7577 (1996).
160 P. Mueller and J. Rocek, J. Am. Chem. Soc., 96, 2836 (1974).
161
H. H. Wasserman and R. W. Murray, eds., Singlet Oxygen, Academic Press, New York, 1979;
A. A. Frimer, Chem. Rev., 79, 359 (1979); A. Frimer, ed., Singlet Oxygen, CRC Press, Boca Raton,
FL, 1985; C. S. Foote and E. L. Clennan, in Active Oxygen in Chemistry, C. S. Foote, J. S. Valentine,
A. Greenberg, and J. F. Liebman, eds., Blackie Academic & Professional, London, 1995, pp. 105–
140; M. Prein and W. Adam, Angew. Chem. Int. Ed. Engl., 35, 477 (1996); M. Orfanopoulos, Molec.
Supramolec. Photochem., 8, 243 (2001).