Palladium-catalyzed synthesis of N-arylated carbazoles using anilines and cyclic diaryliodonium salts

Abstract

SummaryThe direct synthesis of N-arylated carbazoles through a palladium-catalyzed amination of cyclic iodonium salts with anilines is described. In particular, electron-poor aniline derivatives reacted smoothly with only 5 mol % of Pd(OAc)2 as catalyst to give the desired products in up to 71% yield. Furthermore, the reactivity of cyclic iodonium salts is compared with the reactivity of the corresponding cyclic bromonium analogues.

Conversion of 2‐Iodobiaryls into 2,2′‐Diiodobiaryls via Oxidation‐Iodination Sequences: A Versatile Route to Ladder‐Type Heterofluorenes

“…Va rious 2-iodobiaryls (1b-1q)w ere readily oxidized using am ixture of mCPBA( 1.5 equiv) and TfOH (3 equiv) in CH 2 Cl 2 (room temperature,1h), [19,23] thus affording the corresponding cyclic diaryliodonium triflates (2b-2q). Va rious 2-iodobiaryls (1b-1q)w ere readily oxidized using am ixture of mCPBA( 1.5 equiv) and TfOH (3 equiv) in CH 2 Cl 2 (room temperature,1h), [19,23] thus affording the corresponding cyclic diaryliodonium triflates (2b-2q).…”

“…[24] In summary,w eh ave developed ac onvenient two-step method for the preparation of 2,2'-diiodobiaryls from readily accessible 2-iodobiaryls through oxidative cyclization/Cucatalyzed iodinative ring-opening sequences.E ven though cyclic diaryliodonium intermediates have previously been reported to serve as direct precursors to carbazoles and some other bridged biaryl compounds, [19,30] the method presented herein should substantially enhance their utility for the synthesis of aw ide range of heterofluorenes.I ndeed, the versatility of this method has been demonstrated by the preparation of novel tetraiodoteraryls and their conversion into various ladder-type p-conjugated systems.F urthermore, the present method may also be useful for the diversification of Kitas 2,2'-diiodobiaryl-based organocatalysts for oxidation reactions. [24] In summary,w eh ave developed ac onvenient two-step method for the preparation of 2,2'-diiodobiaryls from readily accessible 2-iodobiaryls through oxidative cyclization/Cucatalyzed iodinative ring-opening sequences.E ven though cyclic diaryliodonium intermediates have previously been reported to serve as direct precursors to carbazoles and some other bridged biaryl compounds, [19,30] the method presented herein should substantially enhance their utility for the synthesis of aw ide range of heterofluorenes.I ndeed, the versatility of this method has been demonstrated by the preparation of novel tetraiodoteraryls and their conversion into various ladder-type p-conjugated systems.F urthermore, the present method may also be useful for the diversification of Kitas 2,2'-diiodobiaryl-based organocatalysts for oxidation reactions.…”

“…[16] Even though each synthetic route has its own advantages,t hey also have individual drawbacks.R oute A, for example,a llows the conversion of common 2,2'-dihalobiaryl precursors into avariety of heterofluorenes,but the synthesis of astructurally diverse set of 2,2'-dihalobiaryls is laborious and nontrivial. [18] Herein, we disclose an expansion to route Af or the synthesis of heterofluorenes enabled by the conversion of readily available 2-iodobiaryls (1)into the corresponding 2,2'diiodobiaryls (3)i nt wo steps through oxidation to cyclic diaryliodonium triflates (2), [19] followed by acopper/diaminecatalyzed iodinative ring-opening reaction (Scheme 1b). Consequently, ap ractical solution to enable diversity of both the central heteroatom and the peripheral substituents would be attractive.…”

A mild carbon–boron bond formation from diaryliodonium salts

“…Within this context, Beletskaya reported an exhaustive Suzuki-Miyaura coupling between diaryliodonium salts and sodium tetraphenylborate, 26 Nachtsheim developed two sequential C-N bond forming events of cyclic diaryliodonium salts with anilines to yield N-arylated carbazoles 27 and Greaney recently reported on the use of both aryl groups of diaryliodonium salts in 1,3-difunctionalization of indoles. 28 Indeed, the anticipated reaction sequence comprising the C-B bond formation as a transient path to C-C coupling could be realized.…”

Organohypervalent Iodine Reagents in the Synthesis of Bioactive Heterocycles

“…Various N-arylcarbazoles 188 were synthesized from cyclic iodonium salts 186 and amines 187 through tandem C-N bond formation and Buchwald amination [65]. Various N-arylcarbazoles 188 were synthesized from cyclic iodonium salts 186 and amines 187 through tandem C-N bond formation and Buchwald amination [65].…”