A new route for the synthesis of highly substituted 4-aminoquinoline drug like molecules via aza hetero–Diels–Alder reaction

We have demonstrated for the first time the use of 2H-indazole as a diene partner in an aza hetero–Diels–Alder reaction leading to highly substituted 4-aminoquinolines via a heterocylic–heterocylic (H–H) strategy and have further developed a tandem one-pot method starting from 2-azidobenzaldehyde by the formation of 2C–N, 1N–N and 1C–C bonds. The key features of the present protocol are readily available starting materials, mild reaction conditions, being work-up free and having easy purification. This is the first time where the synthesis of 4-aminoquinoline drug like molecules has been achieved starting from simple starting materials in an atom economical manner.