Generation of Alkyl and Aryl Carbenes

1 Generation of Alkyl and Aryl Carbenes. - A review of recent experimental and theoretical progress in the photochemistry of diazirines has been published. These compounds, unlike their valence isomers, diazo compounds, are relatively stable to most organic reagents and are reasonably stable in dilute solutions, and are therefore useful photochemical and thermal precursors to carbenes. 

The brominated diaryldiazomethane (7) was found to be stable enough to survive Suzuki coupling, thus allowing the synthesis of mono-, bis- and tris(diazo) compounds, e.g. (8). The photoproducts of these diazo compounds were characterized by EPR and SQUID measurements, which indicated that triplet, quintet and septet ground-state species were generated from the mono-, bis- and tris(diazo) precursors, respectively. Temperature-dependent EPR and UV-visible measurements and also laser flash photolysis studies showed that all three species are stable up to 160 K, and have half-lives of a few seconds in solution at room temperature. 

Derivatives of Cgo for photoaffinity labelling studies have been synthesized, including the cis and treats diazirine compounds (21a). The photochemical properties of these are currently being studied in various applications. An 

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