Ligand-Dependant Selective Synthesis of Mono- and Dialkenylcarbazoles through Rhodium(III)-Catalyzed C-H Alkenylation

The C-H alkenylation of N-acetylcarbazoles proceeds smoothly at the C1-position in the presence of a cationic Cp*Rh(III) catalyst to produce 1-alkenylcarbazoles. The use of a cationic (CpRh)-Rh-E(III) catalyst enables further alkenylation to give 1,8-dialkenylcarbazoles. The direct alkenylation procedure in combination with the ready removal of the acetyl directing group provides a straightforward synthetic pathway to 1- and/or 8-alkenyl-N-H-carbazole derivatives. One of 1-alkenyl-N-H-carbazoles obtained by the present C-H alkenylation/deacetylation exhibits solvatochromism.

Automated summary

The C-H alkenylation of N-acetylcarbazoles using a cationic Cp*Rh(III) catalyst at the C1-position results in the formation of 1-alkenylcarbazoles. Further alkenylation is achieved with the use of a cationic (CpRh)-Rh-E(III) catalyst, leading to the formation of 1,8-dialkenylcarbazoles. The direct alkenylation procedure, combined with easy removal of the acetyl directing group, provides a straightforward synthetic route to 1- and/or 8-alkenyl-N-H-carbazole derivatives. One of the 1-alkenyl-N-H-carbazoles obtained in this study exhibits solvatochromism.