Page 1092 - Advanced Organic Chemistry Part B - Reactions & Synthesis

1068 Scheme 12.2. Oxidation of Alcohols with Manganese Dioxide

CHAPTER 12 1 a
CH OH
2
Oxidations CH O
MnO 2
MnO
2 b PhCH CHCH OH 2 PhCH CHCH O
2
70%
MnO
3 c OH 2 CH O
CH 2
61%
4 d O O
MnO 2
CH CH CHCCH CH 3 CH CH CCCH CH 3
2
2
3
3
2
2
OH O
CH 3 OH CH 3 O
5 e MnO 2
HC C C CH CH CH CHCH 3 HC C C CH CH CH CCH3
57%
a. E. F. Pratt and J. F. Van De Castle, J. Org. Chem., 26, 2973 (1961).
b. I. M. Goldman, J. Org. Chem., 34, 1979 (1969).
c. L. Crombie and J. Crossley, J. Chem. Soc., 4983 (1963).
d. E. P. Papadopoulos, A. Jarrar, and C. H. Issidorides, J. Org. Chem., 31, 615 (1966).
e. J. Attenburrow, A. F. B. Cameron, J. H. Chapman, R. M. Evans, B. A. Hems, A. B. A. Janssen, and T. Walker, J.
Chem. Soc., 1094 (1952).
Another recently developed oxidant is CrO , a solid known as Magtrieve™ that
2
is prepared commercially (for other purposes), which oxidizes allylic and benzylic
13
alcohols in good yield. It is also reactive toward saturated alcohols. Because the solid
remains ferromagnetic, it can be recovered by use of a magnet and can be reactivated
by exposure to air at high temperature, making it environmentally benign.
CH 3 CH OH CrO 2 CH 3 CH O
2
CH 3 CH Cl 2 CH 3 90%
2

Another possible alternative oxidant that has recently been investigated is an Fe(VI)
14
species, potassium ferrate, K FeO , supported on montmorillonite clay. This reagent
2 4
gives clean, high-yielding oxidation of benzylic and allylic alcohols, but saturated
alcohols are less reactive.
K FeO 4
2
PhCH OH PhCH O
2
K10 montmorillonite clay
A catalytic system that extends the reactivity of MnO 2 to saturated
secondary alcohols has been developed. 15 This system consists of a Ru(II) salt,
RuCl p-cymene , and 2,6-di-t-butylbenzoquinone.
2 2
13 R. A. Lee and D. S. Donald, Tetrahedron Lett., 38, 3857 (1997).
14 L. Delaude and P. Laszlo, J. Org. Chem., 61, 6360 (1996).
15
U. Karlsson, G. Z. Wang, and J.-E. Backvall, J. Org. Chem., 59, 1196 (1994).