3800
D. C. Whitehead et al. / Tetrahedron Letters 47 (2006) 3797–3800
TM
a
Table 3. OsEnCat recyclability study
5. Cainelli, G.; Contento, M.; Manescalchi, F.; Plessi, L.
Synthesis 1989, 47–48.
. Lee, A. L.; Ley, S. V. Org. Biomol. Chem. 2003, 1, 3957–
3966.
. Ley, S. V.; Ramarao, C.; Lee, A. L.; Ostergaard, N.;
Smith, S. C.; Shirley, I. M. Org. Lett. 2003, 5, 185–
187.
OsEnCatTM
Oxone (4 eq.)
6
7
Ph
Ph
2
2
PhCO H
DMF, 12 h, 25 ºC
TM
Run
OsEnCat (equiv)
Yield (%)
8
. Vanrheenen, V.; Kelly, R. C.; Cha, D. Y. Tetrahedron
Lett. 1976, 1973–1976.
. Pappo, R.; Allen, D. S.; Lemieux, R. U.; Johnson, W. S. J.
Org. Chem. 1956, 21, 478–479.
1
2
3
4
0.02
0.02
0.02
0.02
73
85
56
Inc.
9
1
0. Yu, W. S.; Mei, Y.; Kang, Y.; Hua, Z. M.; Jin, Z. D. Org.
Lett. 2004, 6, 3217–3219.
Note: Inc. = reaction did not proceed to completion after 12 h. Yields
are isolated yields.
After each run, OsEnCat was recovered and reused in the sub-
11. General procedure for the oxidative cleavage of olefins:
The osmium source and Oxone (4 equiv relative to olefin)
were added to DMF (0.2 M based on olefin) at RT.
Osmium loadings varied as follows: 0.01 equiv was
employed when osmium tetroxide, osmium trichloride,
or potassium osmate was employed. Polymer-bound
osmium tetroxide was used in either 0.001 equiv or
a
TM
sequent run without modification.
catalyst loading in the oxidative cleavage of activated
substrates (e.g., trans-stilbene (Table 1, entry 1)).
0
.01 equiv depending on the substrate as indicated in
TM
Table 1. OsEnCat was employed in either 0.0025 equiv
or 0.01 equiv depending on the substrate as indicated in
Table 1. When osmium trichloride or potassium osmate
were employed, the resulting mixture was stirred for 0.5 h
to allow for pre-oxidation of the catalyst, after which time
the olefin (1 equiv) was added in one portion and the
resultant mixture was rotated for 12 h. For all other
osmium sources, the olefin was added directly after the
addition of the osmium source and Oxone. After the
reaction was judged to be complete by TLC, the resulting
mixture was poured into a separatory funnel and the
remaining Os(VIII) was reduced by adding an equal
volume of a saturated sodium sulfite solution. The
resulting slurry was then extracted with ethyl acetate
In summary, the osmium-mediated oxidative cleavage of
olefins is compatible with various different osmium
sources. The ability to employ less volatile and more
innocuous osmium sources without sacrificing yield or
purity of the desired product should serve to enhance
the usefulness of this mild and effective method for the
oxidative cleavage of olefins.
Acknowledgement
The authors thank Professor Ley for kindly providing a
TM
sample of OsEnCat for this study.
(
3·). The combined organics were then washed with 1 N
HCl (3·) and brine, dried over Na SO , and concentrated
2
4
by rotory evaporation. The crude products were purified
by silica gel chromatography or recrystallization where
necessary. Caution: We have noted that these reactions can
become quite exothermic, especially when conducted on a
large scale. For larger scale reactions (greater than 2 mmol
of olefin), we recommend cooling the solution of osmium
source and Oxone on an ice bath before the addition of
olefin and allowing the reaction mixture to warm slowly to
room temperature.
References and notes
1
2
3
4
. Travis, B. R.; Narayan, R. S.; Borhan, B. J. Am. Chem.
Soc. 2002, 124, 3824–3825.
. Schomaker, J. M.; Travis, B. R.; Borhan, B. Org. Lett.
003, 5, 3089–3092.
. Schomaker, J. M.; Borhan, B. Org. Biomol. Chem. 2004, 2,
21–624.
2
6
. Cainelli, G.; Contento, M.; Manescalchi, F.; Plessi, L.
Synthesis 1989, 45–47.
12. Travis, B. R.; Sivakumar, M.; Hollist, G. O.; Borhan, B.
Org. Lett. 2003, 5, 1031–1034.