Transition Metal-Free, Visible Light-Mediated Radical Cyclisation of Malonyl Radicals onto 5-Ring Heteroaromatics

Annulated heteroaromatics can be accessed through the addition of malonyl radicals onto heterocycles. Current methods are applicable to electron-rich heteroaromatics and reliant on transition metals or toxic tin reagents. Here we report a metal-free, visible light-mediated cyclisation of malonates onto 5-ring heteroaromatics using iodomalonates as key intermediates. The iodomalonates are prepared and photolysed in situ to give the desired annulated products, in yields of 46-94% without the need for external catalysts. The scope of this transformation includes N-alkyl, N-acyl and carbon-tethered malonates adding onto a wide range of 5-membered heteroaromatics.

Automated summary

In this study, a metal-free, visible light-mediated cyclization of malonates onto 5-ring heteroaromatics is reported. The method eliminates the need for transition metals or toxic tin reagents and instead utilizes iodomalonates as key intermediates. The annulated products are obtained in good yields (46-94%) without the use of external catalysts.