Metal-free visible-light-promoted thiocyanationicyclization cascade for the synthesis of thiocyanato-containing isoquinolinediones

A visible-light induced metal-free thiocyanate radical addition/intramolecular cyclization cascade reaction for the synthesis of thiocyanato-containing isoquinolinediones from N-alkyl-N-methacryloylbenzamides is described. The organic dye 9-mesityl-10-methylacridinium perchlorate (Acr(+)-Mes ClO4-) is used as a photocatalyst, and cheap and readily available ammonium thiocyanate is used to provide thiocyanate radical by single-electron transfer pathway. The reaction completes the synthesis of C-S and C-C bonds in one pot with abundant molecular oxygen as the sole sacrificial reagent. The method is easy to implement, and 25 new compounds have been prepared in moderate to good yields under mild conditions. This is the first time that a thiocyanate group has been introduced into iso-quinoline-1,3(2H,4H)-diones to construct highly functional drug-like molecules. (C) 2019 Elsevier Ltd. All rights reserved.