Selenium(IV) Oxide-t-Butyl Hydroperoxide1


[7446-08-4]  · O2Se  · Selenium(IV) Oxide-t-Butyl Hydroperoxide  · (MW 110.96) (t-BuOOH)

[75-91-2]  · C4H10O2  · Selenium(IV) Oxide-t-Butyl Hydroperoxide  · (MW 90.14)

(oxidizes alkenes to allylic alcohols or to a,b-unsaturated aldehydes or ketones)

Physical Data: SeO2:2 mp 340 °C. 90% t-BuOOH:3 fp 35 °C; d 0.901 g cm-3. See Selenium(IV) Oxide and t-Butyl Hydroperoxide.

Form Supplied in: SeO2: solid. t-BuOOH: liquid. Commercially available.

Handling, Storage, and Precautions: SeO22 is irritating to the eyes and skin and is highly toxic and corrosive. t-BuOOH1,3 is a flammable liquid and, as with all peroxides, should be handled with care. Use in a fume hood.

Allylic Oxidations.

Selenium(IV) oxide in combination with t-butyl hydroperoxide (TBHP) is an effective system for insertion of oxygen into an allylic carbon-hydrogen bond (eq 1).4 Reaction conditions (CH2Cl2, 0 °C) are much milder than those required for oxidation with selenium(IV) oxide alone and, as a result, yields are higher with fewer oxidation, dehydration, and rearrangement byproducts. Furthermore, the problem of the removal of colloidal selenium is circumvented, and in many cases only catalytic amounts of selenium(IV) oxide are required to effect oxidations in high yields. Over-oxidations to the corresponding aldehyde or ketone products are observed. The rules regarding allylic oxidations by selenium(IV) oxide, proposed by Guillemonat5 and Rapoport,6 apply to these reaction conditions: (1) oxidation occurs at the more highly substituted end of the alkene; (2) the order of reactivity of C-H bonds is CH2 > CH3 > CH (rule 1 takes precedence over rule 2); (3) when the double bond is within a ring, oxidation occurs within the ring; (4) gem-dimethyl trisubstituted alkenes oxidize stereospecifically to give (E)-a-hydroxy alkenes.

Studies of the reaction intermediates suggest that the reaction proceeds via a combination-dissociation-recombination pathway,7 which may explain the double bond migration seen in some selenium(IV) oxide oxidations (eq 2).8

Selenium(IV) oxide supported on silica gel in the presence of TBHP oxidizes methyl allylic sites with no evidence of competing oxidation at methylene allylic positions (eq 3).9

The selenium(IV) oxide-TBHP combination has also been used to oxidize alkenes to their corresponding a,b-unsaturated ketones (eq 4)10 or aldehydes11 using either the standard conditions over extended reaction periods or silica gel-supported selenium(IV) oxide.11a

Oxidation of Alkynes.

Alkynes are similarly oxidized to give a-hydroxy alkynes in good to moderate yields.1 Methine and methylene C-H bonds are more reactive than methyl C-H bonds. Internal alkynes can be oxidized to give alkynediols in good yields with little or no oxidation of the alcohols to ketone products (eq 5).12

Oxidation of Allylic Alcohols.

Selenium(IV) oxide supported on silica gel with TBHP has been used to selectively oxidize primary allylic alcohols to a,b-unsaturated aldehydes in high yields.13 Secondary allylic, benzylic, and saturated alcohols are unaffected by these reaction conditions.

Related Reagents.

t-Butyl Hydroperoxide; Selenium(IV) Oxide.

1. Sharpless, K. B.; Verhoeven, T. R. Aldrichim. Acta 1979, 12, 63.
2. The Merck Index: An Encyclopedia of Chemicals, Drugs, and Biologicals, 11th ed.; Budavari, S., Ed.; Merck: Rahway, NJ, 1989; p 1337.
3. Ref. 2, p 240.
4. Umbreit, M. A.; Sharpless, K. B. JACS 1977, 99, 5526.
5. (a) FF 1967, 1, 992. (b) Guillemonat, A. AC(R) 1939, 11, 143.
6. Bhalerao, U. T.; Rapoport, H. JACS 1971, 93, 4835.
7. Warpehoski, M. A.; Chabaud, B.; Sharpless, K. B. JOC 1982, 47, 2897.
8. Ceccherelli, P.; Curini, M.; Marcotullio, M. C.; Rosati, O. T 1989, 45, 3809.
9. (a) Singh, J.; Sabharwal, A.; Sayal, P. K.; Chhabra, B. R. CI(L) 1989, 533. (b) Chhabra, B. R.; Hayano, K. CL 1981, 1703.
10. Mateos, A. F.; Barrueco, O. F.; González, R. R. TL 1990, 31, 4343.
11. (a) Bock, I.; Bornowski, H.; Ranft, A.; Theis, H. T 1990, 46, 1199. (b) Desai, S. R.; Gore, V. K.; Bhat, S. V. SC 1990, 20, 523. (c) Schreiber, S. L.; Meyers, H. V.; Wiberg, K. B. JACS 1986, 108, 8274.
12. Chabaud, B.; Sharpless, K. B. JOC 1979, 44, 4202.
13. Kalsi, P. S.; Chhabra, B. R.; Singh, J.; Vig, R. SL 1992, 425.

James J. McNally

The R. W. Johnson Pharmaceutical Research Institute, Spring House, PA, USA

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