Diazetine dioxides

Other heterocyclic N-oxides have been found to display biological activities that may depend on their proven or hypothesised ability to release NO these include 4/ /-pyrazol-4-oTie 1,2-dioxides 71, 2H-1,2,3-triazole 1-oxides 72, benzotetrazine 1,3-dioxides 73 and 1,2,3-benzotriazine 3-oxides 74. These systems have been less extensively studied than the furoxan and 1,2-diazetine dioxide systems discussed above. 

Oxidative closure of dioximes leads to diazetine dioxides which can be further reduced in two steps to A -l -diazetines (Scheme 56) (75JOC1409,75KGS748). 

Oxidative closure of l,2-bis(hydroxylamines) 20 leads to diazetine dioxides 21 which can be reduced in two steps to 1,2-diazetines 22 (Scheme 14) <1975JOC1409>. 

Figure 1.16 Possible products from the decomposition of diazetine dioxides 1. (Reproduced with permission from Ref [91].)...

Diazetine dioxides (Fig. 20.10), or cyclic azo dioxides, are four-membered heterocycles prepared by the peroxide-mediated oxidation of the corresponding bis-hydroxy... 

The simple 3,4-dihydro-l,2-diazete 1,2-dioxide (1,2-diazetine 1,2-dioxide, DD) system 53 is unknown. 3,3,4,4-Tetramethyl derivative 54 was the first compound of the class to be synthesised [50]. It has an unusually low triplet energy and is a useful triple quencer [51, 52]. Many other derivatives of 53 have recently been prepared in view of their NO-donor properties. 

The corresponding tetramethyl N,N-dioxide, actually a precursor to the diazetine, has an interesting property in that it is an efficient triplet state quencher. For example, it inhibits the photopinacolization of benzophenone and can be used instead of dienes where wavelengths above 300 nm are employed (72JA5077). 

Oxidation of 2,3-dimethylbutane-2,3-bis-hydroxylamines with bromine or sodium periodate in aqueous solution at room temperature yielded 3,3,4,4-tetramethyl-A1-l,2-diazetine-l,2-dioxide <1972JA5077, 1975JOC1409> which can be reduced to diazetidine. 

Upon ultraviolet irradiation in solution, N,N -nonamethylene-blsdlmethylmaleimide polymerizes into high molecular weight macromolecules with cyclobutane rings in the main chain. The reaction could be sensitized by acetophenone and was quenched by oxygen, ferrocene, and 3,3,4,4-tetramethyl-l,2-diazetine-l,2-dioxide. Stem-Volmer plots were linear for all chromophore concentrations and were dependent on the chromophore concentration. Linear quenching relations can be obtained in the following cases (Scheme IV). 

The topological control of such polymerization reactions has been the subject of recent extensive reviews,52 and the same phenomenon in 2,5-distyrylpyrazine has been further discussed.53 The true photopolymerization process discussed here is typified by the u.v.-induced polymerization of AW -polymethylenebis-(maleimides) discussed above,51 and a complete study of the kinetics of the process is included in this series of papers. The conclusion is reached that the triplet state of the chromophore is the reactive species this can be quenched by the addition of ferrocene or 3,3,4,4-tetramethyl-l,2-diazetine 1,2-dioxide. The kinetics of a further example of true photopolymerization, the reductive photocopolymerization of diaryl ketones, have been compared with those of the photoreduction of the model compound benzophenone and found to be similar.53 The photoreductive poly-recombination of the diaryl ketones shown in Schemes 2 and 3 has been studied extensively.54... 

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