Synthesis of 3-aminotetrahydro-1 H -carbazols by visible-light photocatalyzed cycloaddition of cyclopropylanilines with 2-alkenylarylisocyanides.

A visible-light-induced cycloaddition between 2-alkenylarylisocyanides and cyclopropylanilines is reported. This cascade radical reaction constructs two new C-C bonds and two rings to afford 3-aminotetrahydro-1 H -carbazols with high atom and step economy. The mechanism is rationalized as involving sequential distonic radical cation formation/isocyanide insertion/5- exo -trig cyclization/intramolecular iminium ion addition/tautomerization.