Catalyst- and solvent-free one-pot synthesis of some novel polyheterocycles from aryldiazenyl salicylaldehyde derivatives

A catalyst-and solvent-free domino/Knoevenagel-hetero-Diels-Alder (DKHDA) reaction of two aldyhyde substrates, allyl/prenyl ether tethered aryldiazenylsalicylaldehydes with corresponding pyrazolones and heterocyclic 1,3-diketones is described. Subsequent reduction of aryldiazenylpolyheterocycles, thus obtained in high yields (70-86%), afforded analogues amino frameworks with anticipated biological activity. While in a conventional procedure, no reaction was observed without activation of an allyl-based substrate, an excellent yield was achieved at higher temperature. For a prenyl based substrate, however it underwent smoothly to form a desired cyclised product. The stereochemistry of the compound was confirmed by various NMR experiments and a single crystal X-ray diffraction analysis.