Unified Approach to Pyrazole-Fused Heterocyclic and Carbocyclic Motifs through One-Pot Condensation and Intramolecular Dipolar Cycloaddition Reaction

A one-pot synthesis of highly substituted pyrazoles that are fused to dihydrochromenes, dihydroquinolines and cyclopentane motifs, from readily available precursors is reported. The reaction involves conversion of alkyne-tethered aldehydes into the corresponding tosylhydrazones, base-mediated generation of diazo compounds, and subsequent intramolecular dipolar cycloaddition reaction. A range of internal and terminal alkynes as well as bromoalkyne compounds can be employed as the tethered dipolarophile to afford the corresponding cycloadducts.