Formation and reactions of substituted diazocyclopropanes and cyclopropyldiazonium ions

Article abstract of DOI:10.1023/B:RUCB.0000024855.62916.80

Decomposition of N-nitroso-N-cyclopropylureas at 5-7°C on treatment with K₂CO₃ containing 15-20% H₂O allows simultaneous generation of both substituted diazocyclopropanes and cyclopropyldiazonium ions, which can react according to 1,3-dipolar cycloaddition or azo-coupling pattern with appropriate substrates. The nature of substituents in the cyclopropyl ring have a pronounced influence on the product ratio (and, probably, on the equilibrium between the diazo compound and the diazonium ion). Thus, on treatment with a base in the presence of equimolar amounts of methyl metacrylate as a trap for the diazo compound and 2-naphthol as a trap for the diazonium ion, N-cyclopropyl- and N-(2,2-dimethylcyclopropyl)-N- nitrosourea azo coupling products predominate. Conversely, N-(2,2- dichlorocyclopropyl)-N-nitrosourea is transformed predominantly into 1,3-cycloaddition products. A rationalization for the experimental data is proposed.