1,3-Dipolar Cycloaddition Reactions of Diazopyrazolinones with Electron-Deficient Dipolarophiles

Article abstract of DOI:10.1021/jo00155a028

A study of the reactivity of a series of 4-diazopyrazolin-5-ones toward dipolar cycloaddition with electron-deficient olefinic and acetylenic dipolarophiles has been carried out.Reactions with dimethyl acetylenedicarboxylate afford pyrazolo<1,5-d><1,2,4>triazin-7-ones which result from dipolar cycloaddition followed by a van Alphen-Huttel rearrangement of the initially produced spiro 3H-pyrazole adducts.Reaction with unsymmetrical acetylenic esters afforded variable mixtures of regioisomeric pyrazolotriazinones and 1H-furo<2,3-c>pyrazoles.Product formation has been rationalized in terms of a sustituent-dependent partitioning between spiro 3H-pyrazole adducts and ring-opened diazoalkanes.Spirocarboxylate esters were the only products isolated from reactions with acrylate ester.