Carbazoles aryl-Heck indole-carbazole synthesis

Ackermann employed a different reaction order to meld 1,2-dihaloaryls together with anilines to access a series of carbazoles, including murrayafoline A (Scheme 2, equations 1 and 2) [23]. Jean and colleagues reported a tandem Suzuki/aryl-Heck protocol to prepare functionalized carbazoles and glycosinine (equation 3) [24]. Larock and Liu synthesized a series of carbazoles and the alkaloid muko-nine via an aryl-Heck reaction, which featured an aryne mediated preparation of the requisite diaryl amines [25]. Willis and coworkers reported an indole synthesis involving Heck arylation followed by double bond isomerization (equation 4) [26]. Urabe and colleagues described a similar aryl-Heck indolization from p-bromo-Al-aryl enamines giving 2-alkylindoles [27]. 

The aromatic ring version of the Mori-Ban-Heck indole synthesis can be called an aryl-Heck reaction. This palladium-catalyzed cyclization of o-halo diaryl amines has seen many applications in carbazole and carboline synthesis. 

Zhao and Larock have described the synthesis of carbazoles, indoles, and dibenzofurans 118 via a Ic type cyclization that follows a sequence of Pd-catalyzed cross-coupling of alkynes and aryl iodides 116, then nitrogen-directed palladium migration to an arylpalladium intermediate 117 that undergoes an intramolecular Mizoroki-Heck ring closure <06JOC5340>. 

---