Novel Ag(I)-catalysis of an intramolecular 1,3-dipolar cycloaddition

Article abstract of DOI:10.1016/0040-4039(95)00470-W

Acetylenic α-diazoketones, bearing gem-dimethyl substituents in the α' position, were found to undergo an intramolecular 1,3-dipolar cycloaddition reaction in the presence of silver (I) as catalyst. In that instance, bicyclic pyrazole derivatives were isolated in 47 to 55% yield, even in the conditions of the Arndt-Eistert reaction. The requirement for gem-dimethyl substitution in acyclic substrates is rationalized in terms of steric effects on conformational energies in the transition state.