Mechanistic Studies of a Linear Trisazoalkane, a New Azimine, and a Bicyclic Triaziridine. Azoalkane Homolysis into Seven Fragments

Abstract

An aliphatic azo compound containing three azo groups (1) has been prepared by IF(5) oxidation of beta-azoamine 3. The thermolysis kinetics of this vicinal trisazoalkane were investigated above 155 degrees C, leading to a rate constant only 5.5 times faster than that of the simple model, azo-tert-butane. Because thermolysis to form seven stable products proceeds stepwise, the rate is hardly affected by the high exothermicity of the overall reaction (-93.4 kcal/mol). Oxidation of amine 3 also afforded a cyclic azimine 5 that underwent photolysis to yield a highly strained triaziridine 9 plus an unusual triazane 10, whose structures were elucidated by detailed NMR studies. On standing at ambient temperature, 9 reverted to 5 with a half-life of about an hour.

New Reactions of N‐tert‐Butylimines; Formation of N‐Heterocycles by Methyl Radical Elimination on Flash Vacuum Thermolysis of N‐Benzylidene‐ and N‐(2‐Pyridylmethylidene)‐tert‐butylamines

“…[4] An alternative pathway involves the formation of a tert-butyl radical as a result of homolysis of a tert-butylÀN bond, which is known to take place in tert-butyl azo-compounds. [5] The formation of isobutene from the tert-butyl radical is readily understood, [4b] but formation of NH-imines would seem to require another process. In a previous study, McNab et al [6] described transformations of iminyl radicals into aza-heterocycles under the conditions of FVT.…”

15N NMR spectra, tautomerism and diastereomerism of 4,5-dihydro-1H-1,2,3-triazoles

“…Generally, the 15 N NMR data of 4,5-dihydro-1H-1,2,3triazoles are clearly distinguished from those of cyclic azimines (4,5-dihydro-1H-1,2,3-triazol-2-ium-1-ides) as structurally isomeric compounds 54 and those of open chain triazenes 55 as well.…”

7 Reaction mechanisms. Part (iv) Radical and radical ion reactions

“…Engel et al investigated the thermolysis kinetics of a trisazoalkane, 4.18, and compared the results to the thermolysis kinetics of the simple model azo-tert-butane. 54 They discovered that thermolysis of 4.18 resulted in fragmentation into seven products, and proceeded with a driving force that is ~65 kcal mol 21 greater than that of azo-tert-butane (Scheme 4.18). However, the rate of fragmentation for 4.18 is only 5.5 times greater than that for azo-tert-butane.…”