Transition Metal-Free, Visible Light-Mediated Radical Cyclisation of Malonyl Radicals onto 5-Ring Heteroaromatics
Hernández-Lladó P., Garrec K., Schmitt DC., Burton JW.
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. (Figure presented.).