An expeditious and atom-economic synthesis of lead-like, medicinally important 4,5-dihydropyrazolo[1,5-a]pyrazin-6-ones

We have developed an expeditious and atom-economic synthesis of lead-like, privileged 4,5-dihydropyrazolo[1,5-a]pyrazin-6-ones, which is based on Sonogashira coupling and a two-step condensation with hydrazine hydrate leading to two ring-forming events, with full control over the two elements of diversity present.