Visible-light-mediated Synthesis of Bromo-containing Azaspirotrienediones from N-phenylpropynamides

Graphical A visible light-mediated reaction of N -phenylpropynamide with diethyl 2,2-dibromomalonate has been developed for the synthesis of bromo-substituted azaspirotrienedione. This method avoids the use of transition metals, peroxides and other substances that are harmful to the environment. Through radical addition/ipso-cyclization/oxidation cascade reaction, C−Br, C−C and C=O bonds can be formed in one pot. Various substituents of N -arylpropynamide are well tolerated and yield of the target product is up to 95%. A visible-light-mediated reaction of N -phenylpropynamides with diethyl 2,2-dibromomalonate for the synthesis of bromo-substituted azaspirotrienediones has been developed. This method allows the formation of C−Br, C−C and C=O bonds in one pot via a cascade radical addition/ipso-cyclization/oxidation process. A possible radical mechanism involving single electron transfer and energy transfer processes is proposed based on control experiments, cyclic voltammetry determination and Stern-Volmer quenching experiments.