Since heterocyclic compounds are widely found in pharmaceutical agents as well as bioactive natural products, synthesis of heterocyclic compounds has been a central theme in organic chemistry. The indole skeleton is one of the most important frameworks of heterocyclic compounds and numerous studies on the synthesis have been published. Pyrrolophenanthridinones, which have a condensed 5-6-6-6-tetracyclic skeleton that includes a dihydroindole structure, are also widely found in natural products, particularly Amaryllidaceae alkaloids. Because they possess diverse biological activities, the development of efficient synthetic methods has been a fascinating research topic. However, there are a few practical and mild procedures that fulfilled all the conditions of low temperature, short reaction time and high yield for the construction of indole and pyrrolophenanthridinone skeleton. Samarium(II) diiodide (SmI2) is an important reductant for versatile single electron transfer reactions due to its low toxicity, ease of preparation, tunable reactivity by changing additives, and usefulness under mild reaction conditions. Recently, we have researched on the construction of heterocyclic compounds mediated by SmI2. We have demonstrated a samarium(II)-mediated cyclization reaction of an aryl radical with an allene group in the presence of HMPA and i-PrOH for the facile and mild synthesis of a variety of indole derivatives and with phenyl group in the presence of HMPA for the synthesis of pyrrolophenanthridinone derivatives.

Construction of heterocyclic compounds mediated by samarium(II) diiodide

256th National Meeting (2018)

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