The low-temperature photolysis of diazo compounds. The utility of tertiary alcohol in matrix studies of carbene chemistry.

概要

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Carbene processes within the t-BuOH matrix at −196 °C were investigated in order to show the utility of the matrix as a tool for the study of carbene chemistry. The photolysis of several aryldiazomethane derivatives in the t-BuOH matrix gave the olefinic dimer as the main product, probably arising from a combination of two triplet arylcarbenes in the aggregate of molecules. The similar photolysis of other diazo compounds (e.g., N2CHCOR, R=OR′, NEt2, and Ph) resulted in no detection of the olefinic dimer. This was explained in terms of the structural effect on the ground-state multiplicity of carbene. The photolysis of Ph2CN2 in t-BuOH containing 5% EtOH at −196 °C gave almost exclusively O–H and C–H insertion products with the solute alcohol at the expense of the O–H insertion product with the host, i.e., Ph2CHOBut, which was the major product in the liquidphase photolysis. This is ascribable to the co-aggregation of the carbene precursor with the solute alcohol because of the relatively large guest hole provided by the bulky tertiary alcohol matrix. A more general utility of this matrix was shown in the reaction of Ph2C with Ph2CO to give oxirane, in which the intervention of carbonyl ylide was demonstrated at low temperatures.
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