Controlled Photochemical Synthesis of Substituted Isoquinoline-1,3,4(2)-triones, 3-Hydroxyisoindolin-1-ones, and Phthalimides via Amidyl Radical Cyclization Cascade.

We report a controlled radical cyclization cascade of isoquinoline-1,3,4(2)-triones, 3-hydroxyisoindolin-1-ones, and phthalimides from -alkynylated benzamides by metal-free photoredox catalyzed amidyl N-centered radical addition to the C-C triple bond using the proton-coupled electron transfer (PCET) process under mild reaction conditions. A time tunable synthesis of 3-hydroxyisoindolin-1-ones and phthalimides via β-carbonyl-C(sp) bond cleavage was also achieved under visible light irradiation. A mechanistic rationale for the radical cyclization cascade is supported by various control and quenching experiments as well as EPR studies.