Dimethyl diazirine, decomposition

Attempts to trap dimethylcarbene by photolysis of the 3,3 -dimethyl-diazirine in cyclohexene in the liquid phase were unsuccessful. The evidence for the intermediacy of this carbene thus rests entirely on the analogy of this decomposition with other similar systems. The experimental results obtained can be accounted for equally well if it is assumed that the excited propylene molecules are formed directly from the di-methyldiazirine after the absorption of light. 

The synthesis of 1-aryl-1-chlorocyclopropanes via thermal or photolytic decomposition of 3-aryl-3-chloro-3H-diazirines in the presence of alkenes is described in Houben-Weyl, Vol. El 9b, pp994-996. The preparation of l-chloro-tra A-2,3-dimethyl-l-phenylcyclopropane is described in Houben-Weyl, Vol. El 9 b, p994. 

Addition versus rearrangement of chloro(methyl)-, chloro(ethyl)-, benzyl(chloro)-, chlo-ro(methoxymethyl)- and chloro(isopropyl)carbene generated by photolytic or thermal decomposition of 3-alkyl-3-chloro-3//-diazirines has also been investigated.81 However, it is known that chloro(isopropyl)- or ie/7-butylchlorocarbene does not undergo addition to 2,3-dimethyl-but-2-ene, which is used as a carbene trap. Photolysis or thermolysis of 3-arylmethyl-3-chloro-3//-diazirines in the presence of an alkene has also been studied extensively.84 Addition of the ambiphilic benzylchlorocarbene82 to an alkene to give 1-benzyl-1-chlorocyclopropanes is usually accompanied by its rearrangement to co-chlorostyrene (1,2-hydride shift, for details see ref 83). This isomerization was seriously impeded when the decomposition of 3-benzyl-3-chloro-3//-diazirines was performed in the presence of an alkene,85 with 2,3-dimethylbut-2-ene only traces of co-chlorostyrene were observed.81,86 The results of reactions of benzylchlorocar-benes with some alkenes are collected in Table 6.85... 

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