Phenyl diazomethane, decomposition

The photosensitized decomposition reduces the hydride shift, as may be expected for a triplet species. However, the stereochemical change in the cycloaddition is relatively small. Similieir results were obtained by Baer and Gutsche for the sensitized photolysis of o-n-butyl-phenyl-diazomethane 63... 

The thermal decomposition in acetonitrile is of intermediate order in phenyl-diazomethane between 1 and 2. Thus two reaction paths are operative, one uni-molecular leading to nitrogen and a carbene, and the other bimolecular, involving two molecules of phenyldiazomethane, viz. 

The first example of a cyclopropanation reaction involving a transient phosphorus-substituted carbene was reported in 1967. The copper-catalyzed decomposition of (dimethoxyphos-phoryl)(phenyl)diazomethane in refluxing hept-l-ene gave l-dimethoxyphosphoryl-2-pentyl-l-phenylcyclopropane (1) in 73% yield. No information on the stereochemistry of the cyclopropane 1 was reported. 

Substituted l,2,4-triazoline-3,5-diones are excellent dienophiles which react rapidly at room temperature with oxepins, but particularly with the arene oxide valence tautomer. A similar [4+2] cycloaddition reaction between the episulfide tautomer of thiepin (44) and 4-phenyl-l,2,4-triazoline-3,5-dione has been reported (74AG(E)736>. Benzene episulfide (the valence tautomer of thiepin 44) was generated in situ by thermal decomposition of the diepisulfide (151) at 20 °C and trapped as a cycloadduct at the same temperature (equation 34). A 1,3-dipolar cycloaddition reaction between thiepin (152) and diazomethane has been reported (56CB2608). Two possible cycloadduct products are shown since the final structure has not been unequivocally established (equation 35). 

Carbenes may be generated, among other ways, by the thermal or photochemical decomposition of diazomethane (CH2N2) (Equation II-E) and nitrenes by the thermal decomposition of a suitable azide (R-N3) such as phenyl azide (azidoben-zene [CeHsNs]) (Equation II-F). 

Also obtained by decomposition of l-(2-acetoxy-4-methoxy-phenyl)-2-diazoethanone in methanol with copper bronze for 30 min at 50-55°, followed by hydrolysis of the acetyl derivative (57%). The diazoketone (m.p. 102-105°) was prepared by reaction of diazomethane with 2-acetoxy-4-methoxybenzoyl chloride in ethyl ether for 12 h at -5° [4820]. 

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