Di-t-butyl Peroxyoxalate1

[1876-22-8]  · C10H18O6  · Di-t-butyl Peroxyoxalate  · (MW 234.25)

(useful for clean, low-temperature generation of t-butoxyl radicals;1 induces cyclization of alkenyl hydroperoxides;2 used in radical-trapping experiments,3 and as initiator for alkene autoxidation4 and polymerization5)

Alternate Name: DBPO.

Physical Data: white crystals, mp 50.5-51.5 °C (dec).1a

Solubility: sol most organic solvents (e.g. CH2Cl2, CCl4, PhH, PhCl, and pentane).

Analysis of Reagent Purity: NMR (C6D6, d) 1H: 1.12 (s), 13C: 25.7, 85.4 (no signal is observed for the carbonyl carbon);6 iodometric titration.1a

Preparative Methods: readily obtained by reaction of Oxalyl Chloride with t-butyl hydroperoxide and pyridine in anhydrous pentane.1a,7 It is recommended to collect the crystals of DBPO on a precooled filter (-78 °C).

Handling, Storage, and Precautions: the preparation and manipulation of DBPO must be conducted behind a safety shield. Tongs, gloves, and safety masks should be used throughout every operation. DBPO is highly sensitive to scratching or shock especially when the crystals are dry.1a In one instance, a violent explosion occurred during the transfer of solvent-wetted, recrystallized DBPO from one glass vessel to another.4a,b Consistent with the risk of explosion, it is recommended to use the reagent as prepared. If it must be stored, it should be kept in a flask under Ar at -20 °C or below. Ethers should not be used as solvents since they are known to accelerate perester decomposition.1a For most applications, benzene is the best solvent. Chemists new to the manipulation of organic peroxides are urged to read the appropriate literature before commencing experimental work.8

Thermal Decomposition.

DBPO is a convenient source of t-butoxyl radicals in the temperature range of 20 to 60 °C (eq 1). Its half-life (t1/2) in benzene is about 1470 min at 20 °C and 6.8 min at 60 °C.1a Thermal decomposition is believed to proceed via concerted three-bond cleavage.1,5,9 In low viscosity solvents such as pentane or benzene, about 5% of t-butoxyl radicals are wasted through cage recombination to give di-t-butyl peroxide.10

Peroxyl Radical Cyclizations.

On a per hydrogen basis, t-butoxyl radicals abstract hydrogen 200-1000 times faster from a hydroperoxyl than an allylic methylene or methyl.11 Thus specific peroxyl radicals are accessible on treatment of alkenyl hydroperoxides with DBPO. Intramolecular addition to the alkene, followed by oxygen entrapment of the resultant carbon-centered radical and hydrogen atom transfer, leads to cyclic peroxides.2 By this method, 1,2-dioxolanes (eq 2)12 and 1,2-dioxanes (eq 3)13 are obtained in modest yields. In general, there is a strong bias for exo cyclization2,14,15 and, when there is a choice, the 5-exo-trig mode is preferred over the 6-exo-trig.16 Although DBPO is the most frequently used initiator for these reactions,16,17 Di-t-butyl Hyponitrite is also effective.18 Further, similar transformations have been achieved at -20 to 5 °C with Copper(II) Trifluoromethanesulfonate-octanoic acid in MeCN.19

A mechanistically related approach to 1,2-dioxolanes relies on DBPO-initiated thiol-oxygen cooxidation with 1,4-dienes (eq 4)20 or 1,3,6-trienes.21,14


The use of DBPO in conjunction with an excess of t-Butyl Hydroperoxide (TBHP) allows clean autoxidation of simple alkenes at 30-50 °C to provide allylic hydroperoxides (eq 5).4 The main role of TBHP is to trap product peroxyl radicals as hydroperoxides, thereby preventing side-reactions.4a,b Unlike auto-initiated autoxidation, which often leads to complex mixtures containing many nonperoxide products,4a the DBPO-TBHP procedure is of comparable preparative value to the widely utilized singlet oxygen route.4c

Homolytic Alkylation.

Aldoximes bearing electron-withdrawing groups undergo C-alkylation upon treatment with DBPO in a hydrogen donor solvent at 60 °C (eq 6).22 The alkylation of heteroaromatic compounds with alkyl bromides can be realized in a highly regioselective fashion by using DBPO in conjunction with phenylsilane and Trifluoroacetic Acid (eq 7).23 Other initiators, such as TBHP, 1,1-Di-t-butyl Peroxide, or Dibenzoyl Peroxide, are less effective than DBPO.23

Miscellaneous Applications.

DBPO has been extensively employed as a low-temperature initiator for radical polymerization and related mechanistic studies,5,24 as well as in radical-trapping experiments.3 It is also known to accelerate rearrangement of allylic hydroperoxides25 and to effect oxidative coupling of phenols.26 For an equally useful reagent for producing t-butoxyl radicals at rt and a comparison with DBPO, see Di-t-butyl Hyponitrite.

Related Reagents.

t-Butyl Hydroperoxide; Dibenzoyl Peroxide; Di-t-butyl Hyponitrite; 1,1-Di-t-butyl Peroxide; m-Nitrobenzenesulfonyl Peroxide; p-Nitrobenzenesulfonyl Peroxide.

1. (a) Barlett, P. D.; Benzing, E. P.; Pincock, R. E. JACS 1960, 82, 1762. (b) Singer, L. A. In Organic Peroxides; Swern, D., Ed.; Wiley: New York, 1970; Vol. 1, pp 265-312.
2. Porter, N. A. In Organic Peroxides; Ando, W., Ed.; Wiley: Chichester, 1992; pp 127-139.
3. Beckwith, A. L. J.; Bowry, V. W.; Maod, G. JOC 1988, 53, 1632. Matsuo, M.; Matsumoto, S.; Iitaka, Y.; Niki, E. JACS 1989, 111, 7179. Miura, Y.; Nakamura, Y. BCJ 1990, 63, 1154. Abe, Y.; Seno, S.; Sakakibara, K.; Hirota, M. JCS(P2) 1991, 897. Bottle, S.; Busfield, W. K.; Jenkins, I. D.; Skelton, B. W.; White, A. H.; Rizzardo, E.; Solomon, D. H. JCS(P2) 1991, 1001.
4. (a) Courtneidge, J. L.; Bush, M. CC 1989, 1227. (b) Courtneidge, J. L.; Bush, M. JCS(P1) 1992, 1531. (c) Courtneidge, J. L.; Bush, M.; Loh, L.-S, JCS(P1) 1992, 1539.
5. Moad, G.; Solomon, D. H. In Comprehensive Polymer Science, Allen, G.; Bevington, J. C., Eds.; Pergamon: Oxford, 1989; Vol. 3, pp 97-121.
6. Combs-Walker, L. A.; Hill, C. L. JACS 1992, 114, 938.
7. Lüning, U.; Seshadri, S.; Skell, P. S. JOC 1986, 51, 2071.
8. See for example: Shanley, E. S. In Organic Peroxides; Swern, D., Ed.; Wiley: New York, 1972; Vol. 3, pp 341-364.
9. Bartlett, P. D.; Gontarev, B. A.; Sakurai, H. JACS 1962, 84, 3101.
10. (a) Hiatt, R.; Traylor, T. G. JACS 1965, 87, 3766. (b) Niki, E.; Kamiya, Y. JOC 1973, 38, 1403.
11. Porter, N. A.; Funk, M. O.; Gilmore, D.; Isaac, R.; Nixon, J. JACS 1976, 98, 6000.
12. Carless, H. A. J.; Batten, R. J. TL 1982, 23, 4735.
13. Bloodworth, A. J.; Davies, A. G.; Hay-Motherwell, R. S. JCS(P2) 1988, 575.
14. Beckwith, A. L. J.; Schiesser, C. H. T 1985, 41, 3925.
15. For an exception see: Schiesser, C. H.; Wu, H. AJC 1993, 46, 1437.
16. Bloodworth, A. J.; Curtis, R. J.; Mistry, N. CC 1989, 954.
17. (a) Porter, N. A.; Funk, M. O. JOC 1975, 40, 3614. (b) Porter, N. A.; Zuraw, P. J. JOC 1984, 49, 1345. (c) Carless, H. A. J.; Batten, R. J. JCS(P1) 1987, 1999. (d) Bloodworth, A. J.; Spencer, M. D. TL 1990, 31, 5513.
18. Roe, A. N.; McPhail, A. T.; Porter, N. A. JACS 1983, 105, 1199. See also: Di-t-butyl Hyponitrite.
19. Haynes, R. K.; Vonwiller, S. C. CC 1990, 1102.
20. Beckwith, A. L. J.; Wagner, R. D. JACS 1979, 101, 7099.
21. Beckwith, A. L. J.; Wagner, R. D. CC 1980, 485.
22. Citterio, A.; Filippini, L. S 1986, 473.
23. Minisci, F.; Fontana, F.; Pianese, G.; Yan, Y. M. JOC 1993, 58, 4207.
24. Examples: Bisfield, W. K.; Grice, D. I.; Jenkins Bottle, S.; Busfield, W. K.; Jenkins, I. D.; Thang, S.; Rizzardo, E.; Solomon, D. H. Eur. Polym. J. 1989, 25, 671. Moad, G.; Rizzardo, E.; Solomon, D. H.; Beckwith, A. L. J. Polym. Bull. 1992, 29, 647.
25. Dang, H.-S.; Davies, A. G.; Davison, I. G. E.; Schiesser, C. H. JOC 1990, 55, 1432.
26. Armstrong, D. R.; Cameron, C.; Nonhebel, D. C.; Perkins, P. G. JCS(P2) 1983, 563.

John Boukouvalas

Université Laval, Québec, Canada

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