Page 1164 - Advanced Organic Chemistry Part B - Reactions & Synthesis

1140 considerable success involves oxidation in the presence of a trialkyl phosphite. 243 The
intermediate hydroperoxide is efficiently reduced by the phosphite ester.
CHAPTER 12
Oxidations O O
O OCH 3 NaO-t-Bu, O OCH 3
CCH 3 O , DMF CCH 3
2
OH
P(OEt) 3
O OCH 3 O OCH 3
55% Ref. 144

This oxidative process has been successful with ketones, 244 esters, 245 and lactones. 246
Hydrogen peroxide can also be used as the oxidant, in which case the alcohol is
formed directly. 247 The mechanisms for the oxidation of enolates by oxygen is a radical
chain autoxidation in which the propagation step involves electron transfer from the
carbanion to a hydroperoxy radical. 248

O – O
RC CR 2 +O 2 RC CR 2 +O 2 – .
.
O O
RCCR 2 + O 2 RCCR 2
.
O O ·
O – O O O
RC CR 2 + RCCR 2 RC CR 2 + RCCR 2
.
O O · O O –
Arguments for a nonchain reaction between the enolate and oxygen to give the
hydroperoxide anion directly have been advanced as well. 249
The silyl enol ethers of ketones are also oxidized to -hydroxy ketones by
m-chloroperoxybenzoic acid. If the reaction workup includes acylation, -acyloxy
ketones are obtained. 250 These reactions proceed by initial epoxidation of the silyl enol
ether, which then undergoes ring opening. Subsequent transfer of either the O-acyl or
O-TMS substituent occurs, depending on the reaction conditions.

OSi(CH 3 ) 3 (CH 3 ) 3 SiO RCO 2 OSi(CH 3 ) 3 O O
O
OH OSi(CH 3 ) 3 O 2 CR
RCO 3 H RCO 2 H
or
243 J. N. Gardner, F. E. Carlon, and O. Gnoj, J. Org. Chem., 33, 3294 (1968).
244
F. A. J. Kerdesky, R. J. Ardecky, M. V. Lashmikanthan, and M. P. Cava, J. Am. Chem. Soc., 103, 1992
(1981).
245
E. J. Corey and H. E. Ensley, J. Am. Chem. Soc., 97, 6908 (1975).
246 J. J. Plattner, R. D. Gless, and H. Rapoport, J. Am. Chem. Soc., 94, 8613 (1972); R. Volkmann,
S. Danishefsky, J. Eggler, and D. M. Solomon, J. Am. Chem. Soc., 93, 5576 (1971).
247
G. Buchi, K. E. Matsumoto, and H. Nishimura, J. Am. Chem. Soc., 93, 3299 (1971).
248
G. A. Russell and A. G. Bemix, J. Am. Chem. Soc., 88, 5491 (1966).
249 H. R. Gersmann and A. F. Bickel, J. Chem. Soc. B, 2230 (1971).
250
G. M. Rubottom, J. M. Gruber, R. K. Boeckman, Jr., M. Ramaiah, and J. B. Medwick, Tetrahedron
Lett., 4603 (1978); G. M. Rubottom and J. M. Gruber, J. Org. Chem., 43, 1599 (1978); G. M. Rubottom,
M. A. Vazquez, and D. R. Pelegrina, Tetrahedron Lett., 4319 (1974).