Decomposition of meso- and dl-3,4-diethyl-3,4-dimethyldiazetine (a 1,2-diaza-1-cyclobutene)

Abstract

Decomposition of meso-and d/-3,4-Diethyl-3,4-dimethyldiazetine (a 1,2-Diaza-l -cyclobutene)1 Sir:Study of the thermal decomposition of diazenes (azo compounds) has provided much information on the nature of diradicals and on the question of concerted vs. stepwise decomposition paths.2 The four-membered-ring diazene-the 1,2-

Thermal Decomposition of a Series of 1,2-Diazetines

“…1,2-Diazetines are a class of strained four-membered ring azo compounds . Diazetines are quite thermally robust, despite the release of strain energy that would be anticipated upon decomposition (eq 1). , Thus, although decomposition to afford N 2 and the corresponding alkene is strongly exothermic (Δ H ≈ −50 kcal/mol), there is a substantial activation barrier to the process (Δ H ⧧ ≈ 35 kcal/mol) . The high activation barrier was initially attributed to one of two factors: (i) the significant energy “cost” required to surmount the symmetry forbiddenness of a [2s + 2s] cycloreversion or (ii) the large increase in strain energy for the molecule to adopt a transition-state geometry required for a symmetry-allowed [2s + 2a] cycloreversion .…”

“…The high activation barrier was initially attributed to one of two factors: (i) the significant energy “cost” required to surmount the symmetry forbiddenness of a [2s + 2s] cycloreversion or (ii) the large increase in strain energy for the molecule to adopt a transition-state geometry required for a symmetry-allowed [2s + 2a] cycloreversion . An alternative, nonconcerted process was later suggested in which one C−N bond is broken to form a biradical intermediate followed by loss of the remaining N 2 fragment . A crucial piece of mechanistic evidence was provided by the work of Greene who demonstrated that diazetine 2 stereospecifically afforded alkene 3 via cis elimination of N 2 .…”

Construction of 3,4‐dihydro‐1,2‐diazete ring through 4π electron cyclization of 4‐hydroxy‐2‐oxo‐2H chromene‐3‐carbaldehyde [(1E)‐arylmethylene] hydrazone

“…1,2‐Diazetine N , N ‐dioxides (diazetine dioxides) are a class of strained four‐membered ring azo dioxide heterocycles. Although the first report of a diazetine dioxide was as early as 1971, only a handful of such compounds are currently known [5–9]. Diazetine dioxides have been used as highly effective low‐energy triplet quenchers in photochemical reactions [10] and have been recently investigated for their biological activity as potent vasorelaxant and antiaggregant agents [7–9, 11].…”

Thermal Decomposition of meso- and d,l-3,4-Diethyl-3,4-dimethyldiazetine N,N‘-Dioxide

“…The stereochemically defined diazetine dioxides 1c and 1d have been briefly reported in the literature as synthetic intermediates, but their decomposition was apparently not investigated . We synthesized compounds 1c and 1d according to literature procedures that generally mirrored the synthesis of the well-known tetramethyl derivative 1b (Scheme ) .…”