Page 1158 - Advanced Organic Chemistry Part B - Reactions & Synthesis

1134 -Hydroxyketones can be obtained from silyl enol ethers by oxidation using a catalytic
amount of OsO with an amine oxide serving as the stoichiometric oxidant. 220
4
CHAPTER 12
Oxidations CH
CH 3 3
OsO 4
(CH ) SiO OSiR 3 O – O OSiR 3
3 3
O + N
CH 3 HO CH 3
CH 3
Ref. 221
Other procedures for -oxidation of ketones are based on prior generation of
the enolate. Among the reagents used is a molybdenum compound, MoO -pyridine-
5
HMPA, which is prepared by dissolving MoO in hydrogen peroxide, followed by
3
addition of HMPA. This reagent oxidizes the enolates of aldehydes, ketones, esters,
and lactones to the corresponding -hydroxy compound. 222

O O
CH O CH O
H C H 3 C OH
3
O 1) LDA O
2) MoO -pyridine
5
HMPA
CH 3 CH H CH 3 H
CH 3
85%
3
Ref. 223
12.5.2. Oxidation of Ketones and Aldehydes by Oxygen and Peroxidic
Compounds

12.5.2.1. Baeyer-Villiger Oxidation of Ketones. In the presence of acid catalysts,
peroxy compounds are capable of oxidizing ketones by insertion of an oxygen atom
into one of the carbon-carbon bonds at the carbonyl group. Known as the Baeyer-
Villiger oxidation, 224 the mechanism involves a sequence of steps that begins with
addition to the carbonyl group, followed by peroxide bond cleavage with migration to
oxygen.

O O O
O H
RCR + R′COOH RC R RCOR + R′CO H
2
O O C O
R′

220
J. P. McCormick, W. Tomasik, and M. W. Johnson, Tetrahedron Lett., 22, 607 (1981).
221 R. K. Boeckman, Jr., J. E. Starrett, Jr., D. G. Nickell, and P.-E. Sun, J. Am. Chem. Soc., 108, 5549
(1986).
222
E. Vedejs, J. Am. Chem. Soc., 96, 5945 (1974); E. Vedejs, D. A. Engler, and J. E. Telschow, J. Org.
Chem., 43, 188 (1978); E. Vedejs and S. Larsen, Org. Synth., 64, 127 (1985).
223 S. P. Tanis and K. Nakanishi, J. Am. Chem. Soc., 101, 4398 (1979).
224
C. H. Hassall, Org. React., 9, 73 (1957); G. R. Krow, Org. React., 43, 252 (1993); M. Renz and
B. Beunier, Eur. J. Org. Chem., 737 (1999); G.-J. ten Brink, I. W. C. E. Arends, and R. A. Sheldon,
Chem. Rev., 104, 4105 (2004).