Di-t-butyl Hyponitrite1

[14976-54-6]  · C8H18N2O2  · Di-t-butyl Hyponitrite  · (MW 174.24) (E)


(a convenient, low-temperature source of t-butoxyl radicals;1 induces serial cyclization of polyunsaturated hydroperoxides,2 rearrangement of allylic hydroperoxides,3 and reduction of alkyl halides or dialkyl sulfides with Et3SiH;4 used in radical-trapping experiments;5 and as initiator for dimerization6 and polymerization7)

Alternate Names: DTBN; TBHN; DBH.

Physical Data: white crystals mp 84.5 °C (dec);1d volatile (0.1 mmHg at rt).1a

Solubility: insol H2O; sol common organic solvents (e.g. hexane, benzene, toluene, CCl4, and EtOH).

Analysis of Reagent Purity: NMR (CDCl3, d) 1H 1.33 (s); IR (cm-1) 2959, 1368, 1183, 995;1a for IR and Raman band assignments, see Ogle et al.;8 UV (lmax, pentane) 223.4 nm (ε 7140 M-1 cm-1);1d the trans structure has been established by X-ray analysis.8

Preparative Method: obtained in 80-90% yield by reaction of sodium hyponitrite with t-BuBr in the presence of Iron(III) Chloride or Zinc Chloride.9 The preparation of sodium hyponitrite (from Na, benzophenone, and nitric oxide)10a must be performed with extreme care.10b

Handling, Storage, and Precautions: although DTBN appears to be insensitive to scratching and is considered as safe,1a it can detonate when struck.1d Mixtures of DTBN with formamides undergo violent reaction or explosion when heated at 60-70 °C.6 Due to the potential risk of explosion, it is strongly recommended that all operations involving DTBN be carried out behind a safety shield using tongs, gloves, and a safety mask. Since DTBN is quite volatile, most of the unchanged material can be conveniently removed at the end of a reaction by flushing the mixture with N2 or Ar.5,11a Solid DTBN can be kept intact for several months at -10 °C or below.

Thermal Decomposition.

DTBN is used as a clean source of t-butoxyl radicals in the temperature range of 20 to 90 °C (eq 1).1b Decomposition probably involves a simultaneous two-bond scission.1c,d In low viscosity solvents, 4-10% of t-butoxyl radicals are wasted through cage recombination to form di-t-butyl peroxide.1a,b Compared to Di-t-butyl Peroxyoxalate (DBPO), which also delivers t-butoxyl radicals at rt, DTBN decomposes more slowly and is far less sensitive to shock or scratching.1a From published data,1a the half-life (t1/2) of DTBN in isooctane is calculated to be ca. 425 min at 45 °C (t1/2 of DBPO at 45 °C in benzene is about 44 min).12 Unlike DBPO, DTBN is resistant to induced decomposition in both protic and aprotic solvents even at high concentrations.1a

Peroxyl Radical Serial Cyclizations.

In the presence of DTBN and oxygen, polyunsaturated hydroperoxides undergo multiple cyclizations to form polycyclic peroxides.2,13 Thus compound (1) cyclizes by a 6-exo-trig mode to afford, after selective reduction of the resulting hydroperoxides (2), five diastereomeric hydroxy-bis-1,2-dioxanes (3) in nearly 70% overall yield (eq 2).2 Similarly, bis-1,2-dioxolanes are accessible from suitable substrates through a 5-exo closure.13 For a more detailed discussion and further examples of peroxyl radical cyclizations, see Di-t-butyl Peroxyoxalate.

Allylic Hydroperoxide Rearrangement.

The [2,3]-rearrangement of allylic hydroperoxides is catalyzed by radical initiators or by light.3 With few exceptions,14 DTBN is particularly effective in accelerating the process at 20-40 °C.3,15 Rearrangement is highly stereoselective at rt, as illustrated by the transformation of (4) (>99% ee) into a 1.7:1 mixture of (4) and (5), which are obtained with ee's of 97-99% (eq 3).15a Both experimental15b and theoretical16 results suggest that an allyl radical-dioxygen pair is involved.

Radical Chain Reductions.4

Saturated primary, secondary, or tertiary alkyl halides undergo essentially quantitative reduction to the corresponding alkanes upon treatment with DTBN, Triethylsilane, and t-dodecanethiol (mixture of isomers). An example is shown in eq 4. Likewise, dialkyl sulfides are reduced to alkanes in excellent yields. The thiol acts as a polarity reversal catalyst which mediates hydrogen-atom transfer from the silane to the alkyl radical.

Miscellaneous Applications.

In several cases, dimerization of organic compounds can be achieved in better yields by using DTBN instead of conventional initiators such as 1,1-Di-t-butyl Peroxide or acetyl peroxide (eq 5).6

DTBN is also used as an initiator for autoxidation,11 radical polymerization,7,17 and in radical-trapping experiments.5

Related Reagents.

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

1. (a) Kiefer, H.; Traylor, T. G. TL 1966, 6163. (b) Kiefer, H.; Traylor, T. G. JACS 1967, 89, 6667. (c) Neuman R. C., Jr.; Bussey, R. J. JACS 1970, 92, 2440. (d) Chen, H.-T. E.; Mendenhall, G. D. JACS 1984, 106, 6375.
2. (a) Porter, N. A.; Roe, A. N.; McPhail, A. T. JACS 1980, 102, 7574. (b) Roe, A. N.; McPhail, A. T.; Porter, N. A. JACS 1983, 105, 1199.
3. (a) Porter, N. A.; Sullivan Wujek, J. JOC 1987, 52, 5085. (b) Beckwith, A. L. J.; Davies, A. G.; Davidson, I. G. E.; Maccoll, A.; Mruzek, M. H. JCS(P2) 1989, 815.
4. Cole, S. J.; Kirwan, J. N.; Roberts, B. P.; Willis, C. R. JCS(P1) 1991, 103.
5. Examples: Baban, J. A.; Roberts, B. P. JCS(P2) 1986, 1607. Bowry, V. W.; Ingold, K. U. JACS 1992, 114, 4992.
6. Protasiewicz, J.; Mendenhall, G. D. JOC 1985, 50, 3220.
7. Moad, G.; Solomon, D. H. In Comprehensive Polymer Science; Allen, G.; Bevington, J. C., Eds.; Pergamon: Oxford, 1989; Vol. 3, pp 97-121.
8. Ogle, C. A.; VanderKooi, K. A.; Mendenhall, G. D.; Lorprayyoon, V.; Cornilsen, B. C. JACS 1982, 104, 5114.
9. (a) Mendenhall, G. D. TL 1983, 24, 451. (b) Banks, J. T.; Scaiano, J. C.; Adam, W.; Schulte Oestrich, R. JACS 1993, 115, 2473.
10. (a) Mendenhall, G. D. JACS 1974, 96, 5000. (b) Mendenhall, G. D.; Stewart, L. C.; Scaiano, J. C. JACS 1982, 104, 5109.
11. (a) Barclay, L. R. C.; Ingold, K. U. JACS 1981, 103, 6478. (b) Porter, N. A.; Mills, K. A.; Carter, R. L. JACS 1994, 116, 6690.
12. Bartlett, P. D.; Benzing, E. P.; Pincock, R. E. JACS 1960, 82, 1762.
13. Khan, J. A.; Porter, N. A. AG(E) 1982, 21, 217.
14. Dang, H.-S.; Davies, A. G.; Davison, I. G. E.; Schiesser, C. H. JOC 1990, 55, 1432.
15. (a) Porter, N. A.; Kaplan, J. K.; Dussault, P. H. JACS 1990, 112, 1266. (b) Porter, N. A.; Mills, K. A.; Caldwell, S. E.; Dubay, G. R. JACS 1994, 116, 6697.
16. Boyd, S. L.; Boyd, R. J.; Shi, Z.; Barclay, L. R. C.; Porter, N. A. JACS 1993, 115, 687.
17. Yamada, B.; Yoshikawa, E.; Otsu, T. Polymer 1992, 33, 3245.

John Boukouvalas

Université Laval, Québec, Canada

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