Insecticidal lead identification by screening benzopyrano[4,3-c]pyrazol-3(2H)-ones library constructed from multiple-parallel synthesis under microwave irradiation

A rapid library-generation via liquid-phase multiple-parallel synthesis of 2-(substituted)benzyl-1-benzopyrano[4,3-c]pyrazol-3(2H)-ones, bearing two points of diversity, under microwave irradiation was successfully performed using chromenone-3-carboxylic acids as starting materials. Compared to an identical library generated by conventional parallel synthesis, microwave-assisted parallel synthesis dramatically decreased reaction times from an average of 16 h to 13 min, and the yields of products and intermediates were improved in most cases. A bioassay indicated that the compounds of the library exhibited excellent insecticidal activity against T. cinnabarinus at the dosage of 250 mg L-1, and some compounds still exhibited insecticidal activity when the dosage was reduced to 50 mg L-1. This shows that 2-(substituted) benzyl-1-benzopyrano[4,3-c]pyrazol-3(2H)-ones might be used as lead structures for further optimization. To our knowledge, this is the first report about the application of solution-phase multiple-parallel synthesis under microwave irradiation to construct libraries of benzopyrano-[4,3-c]pyrazol-3(2H)-ones with insecticidal activity. The coupling of microwave technology with liquid-phase parallel synthesis constitutes a novel and particularly attractive avenue for the rapid generation of structurally diverse libraries for lead discovery. (c) 2006 Elsevier Ltd. All rights reserved.