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.

一种新型的光诱导三组分反应已被开发，该反应涉及氰基芳烃、烯烃和N-保护的吡咯。此反应通过引入吡咯作为中性碳中心亲核试剂，扩展了光NOCAS反应的适用范围。所使用的氰基芳烃包括四氰基苯（TCB）、2,3,5,6-四氟-1,4-二氰基苯（TFDCB）和1,4-二氰基苯（DCB）。N-甲基、N-苯基和N-Boc吡咯是该反应中适宜的亲核试剂。利用TCB单重激发态的强电子受体能力，多种烯烃参与了该反应，包括高度电子缺乏的4-氟基、4-氯基、2,3,4,5,6-五氟基苯乙烯和N-甲基马来酰亚胺，从而实现了烯烃的1,2-二芳基化和吡咯环的2-烷基化，这一过程通过三个反应物之间顺序形成两个新的C-C键来完成。