Phosphine-Free [3+2] Cycloaddition of Propargylamines with Dialkyl Azodicarboxylates: An Efficient Access to Pyrazole Backbone

A phosphine-free [3+2] cycloaddition reaction of the substituted propargylamines with dialkyl azodicarboxylates at room temperature is described. This reaction provides a new approach to functionalized pyrazoles in good yields and high selectivity.