One-pot synthesis of polyfunctional pyrazoles: an easy access to α-diazoketones from arylglyoxal monohydrates and tosylhydrazine

A new and efficient method for the generation of alpha-diazoketones has been developed from arylglyoxal monohydrates and tosylhydrazine at room temperature. 1,3-Dipolar cycloaddition reactions were used to constructing polyfunctional pyrazole derivatives by the reaction of generated alpha-diazoketones in situ with electron-deficient alkenes, quinones and coumarins in one pot. The one-dimensional molecular packing of 1H-benzo[f]indazole-4,9-dione derivatives along the c direction demonstrated a helical chain formation via N-H center dot center dot center dot O hydrogen-bonding. (C) 2014 Elsevier Ltd. All rights reserved.