A three-component reaction by photoinduced electron transfer mechanism with N-protected pyrroles as neutral carbon nucleophiles

A new photoinduced three-component reaction between a cyanoarene, an alkene and an N-protected pyrrole has been developed. This reaction extended the scope of the photo-NOCAS reaction by introducing pyrrole as a neutral carbon-centered nucleophile. The cyanoarenes used include tetracyanobenzene (TCB), 2,3,5,6-tetrafluoro-1,4-dicyanobenzene (TFDCB) and 1,4-dicyanobenzene (DCB). N-Methyl, N-phenyl and N-Boc pyrroles are suitable nucleophiles in the reaction. Taking advantage of the strong electron acceptor ability of the singlet excited TCB, a wide range of alkenes, including the highly electron deficient 4-fluoro-, 4-chloro-, 2,3,4,5,6-pentafluorostyrenes and N-methylmaleimide take part in this reaction, leading to the simultaneous 1,2-diarylation of the alkene and the regioselective 2-alkylation of the pyrrole ring via sequential formation of two new C-C bonds between the three reactants.