NOVEL AG(I)-CATALYSIS OF AN INTRAMOLECULAR 1,3-DIPOLAR CYCLOADDITION

Acetylenic alpha-diazoketones, bearing gem-dimethyl substituents in th e alpha' position, were found to undergo an intramolecular 1,3-dipolar cycloaddition reaction in the presence of silver(ll as catalyst. In t hat instance, bicyclic pyrazole derivatives were isolated in 47 to 55% yield, even in the conditions of the Arndt-Eistert reaction. The requ irement for gem-dimethyl substitution in acyclic substrates is rationa lized in terms of steric effects on conformational energies in the tra nsition state.