Di-tert -butyl hyponitrite

Di-/er/-butyl hyponitrite See /rans-Di-tert-butyl hyponitrite Formamides... 

Allyloxysilanes (14) undergo radical chain cyclization in the presence of di-tert-butyl hyponitrite as radical initiator and thiol as a catalyst at ca 60 °C (Reaction 6.3) [5]. The thiol promotes the overall abstraction from the Si—H moiety as shown in Scheme 6.4 and the silyl radical undergoes a rapid 5-endo-trig cyclization. Indeed, EPR studies on the reaction of t-BuO radical with silanes 14 detected only spectra from the cyclized radicals even at — 100°C, which implies that the rate constants for cyclization are > 10 s at this temperature. 

The strength of the O H bond in ROO-H is comparable to that of allylic and benzylic C—H bonds and is ca 15-20 kcal mol 1 weaker than the corresponding RO—H bond158. Therefore, alkoxy radicals like r-BuO are suitable initiators in reactions of the type described in Scheme 37. The hazardous di-fert-butyl peroxalate (DBPO)159 (t /i ca 12 h at 20 °C in solution) (equation 9) and the safer di-tert-butyl hyponitrite (DTBN) (t /2 ca 12 h at 40 °C) (equation 10)1 60, 161 have been widely used for the generation of tert-BuO radicals under very mild conditions155 158. 

Dibutyl hyponitrite, 3064 fra/ ,v-Di-tert-butyl hyponitrite, 3065 Diethyl hyponitrite, 1684 Diisopropyl hyponitrite, 2533 Dimethyl hyponitrite, 0909 Dipropyl hyponitrite, 2534 See related AZO COMPOUNDS... 

The efficient reductions observed for various organic halides when treated with Et3SiHin two-fold excess in the presence of catalytic amounts of a thiol and di-tert-butyl hyponitrite as initiator confirmed the validity of this approach. Silane-thiol couples were also used, in boiling octane with di-terf-butyl peroxide as initiator, for the reduction of the methylxanthate of 1,2 5,6-di- O -isopropylidene-a-D-glucofuranose, to yield the corresponding deoxy sugar in 60%173 and 70%174... 

From Porter etal. (1994) oxidation of methyl oleate in hexane solution inititated with di-tert-butyl hyponitrite products analysed as the hydroxyoctadecenoates by normal phase HPLC. Co-oxidation of oleate with tert-butyl hydroperoxide produced only the W-cis, 9-trans,10-transand 8-cis in a ratio of 1 1.2 for ll-cis 9-trans and i-cis 0-trans products. 

Di(<9—O-tert-butyl) ethyl diperoxophosphate, 3368 Di-ferf-butylfluorophosphine, 3062 Dibutyl hydrogen phosphite, 3080 Dibutyl hyponitrite, 3064 fraws-Di-ferf-butyl hyponitrite, 3065a Dibutylmagnesium, 3063 Dibutyl-3-methyl-3-buten- 1-ynlborane, 3612a... 

This rearrangement proceeds via a 2,3-peroxy radical mechanism4,5 24. Radicals are probable intermediates as these reactions are initiated or accelerated by light or free radical sources (benzyl peroxides, tert-butyl hyponitrite) 2 6, are inhibited by radical scavengers (4-methyl-2,6-di-/ert-butyl phenol)6,7, and display ESR signals of allyl peroxy radicals7-9. 

Of considerable practical importance is the concentration of substrate. Even fairly reactive compounds do not autoxidize readily at sub-millimolar concentrations [7a]. The rate of initiation is also crucial in promoting autoxidation. Although many autoxidation reactions are auto-initiated, the use of initiators such as d -tert-butyl peroxyoxalate (DBPO) [12a] or di-tcr -butyl hyponitrite (DTBN) [12b] can be beneficial. DBPO and DTBN are convenient sources of tcrt-butoxyl radicals in the temperature ranges of 20-60 and 20-90 °C, respectively (Scheme 2). They are especially effective when used in conjunction with an excess of tcrt-butyl hydroperoxide (TBHP), whose role is to trap product peroxyl radicals as hydroperoxides, thereby preventing side-reactions [13a,c. In contrast to auto-initiated autoxidation, the autoxidation of simple alkenes (e.g. 1-methylcyclohexene, Scheme 2) by the DBPO-TBHP procedure is of comparable preparative value to the widely used singlet oxygen route [13a,b]. 

Figure 13. Fc vs. fluidity for di-tert-butyl peroxide from the hyponitrite (9)...

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