Triazole carbene, rearrangements with

This degenerate rearrangement has not been observed with 5-dia-zomethyl-l,4-diphenyl-l,2,3-triazole. The diazo function decomposes and the carbene formed reacts, when benzene is used as solvent, into a cyclo-heptatriene. The requirement to have the ester function present at C-4 apparently has to do with stabilization of the diazo function. 

Triazoles also serve as a precursor of metal carbene complexes. For instance, Murakami and Fokin independently reported a denitrogenative rearrangement reaction of triazolyl alcohol 69 (Scheme 7.27) [41]. The ring-chain tautomeriza-tion of 69 generates its diazo imine form, which reacts with Rh2(Oct)4 to produce a rhodium carbene complex. The following 1,2-alkyl migration and elimination of rhodium produce enaminone 70. 

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