Rh(III)-Catalyzed Oxidative C–H Activation/Domino Annulation of Anilines with 1,3-Diynes: A Rapid Access to Blue-Emitting Tricyclic N,O-Heteroaromatics

Abstract

Disclosed herein is a rhodium-catalyzed oxidative C–H activation/domino annulation of N-Boc-anilines with 1,3-diynes for the construction of tricyclic N,O-heteroaromatics. This reaction features easily available substrates, mild reaction conditions, high regioselectivity, mono/diannulation selectivity, and intra/intermolecular annulation selectivity. Moreover, this synthetic protocol enables the rapid assembly of a library of blue-emitting molecules with high quantum yields, among of which two fluorophores with pure blue-emission in toluene are discovered.

Recent Advances in the Synthesis of 5‐MemberedN‐Heterocycles via Rhodium Catalysed Cascade Reactions

“…Then, a cyclic organorhodium complex D was generated via π-coordination and migratory insertion of the 1,3-diyne 191, followed by a reductive elimination delivering an indole derivative E, the intramolecular cyclization of which led to the desired product 192 (Scheme 55). [116] Heterocycles featuring N-fused saturated bicycles has its importance in bioactive natural products. Indolizidine-type alkaloids such as astanospermine, gephyrotoxin and rhazinilam display a wide array of biological activity including antiviral, CNS modulation, and anticancer properties respectively.…”

“…Rh(III)-catalyzed oxidative CÀ H activation/domino annulation of anilines with 1,3-diynes to access a fused tricyclic N,O-heteroaromatics. [116] ChemistrySelect alkenylation/DG migration and [3 + 2] annulation, respectively. The mechanistic steps include formation of rhodacycle A by directing group-assisted CÀ H activation of 199, followed by regioselective coordination and migratory insertion of 1,3diynes into the RhÀ C bond generating an intermediate B; Subsequent cascade intramolecular nucleophilic addition, CÀ N bond cleavage and proto-demetalation afforded 1,3-enynes 201 which under cyclization in presence of CsOAc resulted into pyrrolo [1,2-a]indoles 202 (Scheme 57).…”

Transition Metal-catalyzed C-H /C-C Activation and Coupling with 1, 3-diyne

“…In 2020, Yudong Yang group developed a Rh(III) catalyzed C-H activation/domino annulation strategy to synthesize blue-emitting fused tricyclic N,O-heteroaromatics (Scheme 36). 23 Reaction of N-Boc anilines 46 with 1,3-diynes 47 in presence of [Cp*RhCl2]2 as a catalyst, AgSbF6 and PivOH as an additive, and Ag2O as an oxidant in DCE at 60 °C provided an excellent yield of the product 48. In this protocol exclusive fused heteroaromatic skeleton has been observed rather than bis-heteroaromatic skeletons.…”

Traceless Bidentate Directing Group Assisted Cobalt-Catalyzed sp2-C–H Activation and [4 + 2]-Annulation Reaction with 1,3-Diynes

“…1,3-Diynes are easily accessible synthetic scaffolds, and found application in the synthesis of various arenes, heteroarenes, and natural products . However, their use in transition metal catalyzed C–H bond functionalization/annulation reactions for accessing alkynylated heterocycles is confined to only a handful of examples . This is due to the challenges in controlling the chemo- and regioselectivity for the migratory insertion of the organometallic species with the 1,3-diynes .…”

“…We next focused on the formerly intended double C–H activation/annulation with 1,3-diynes for the synthesis of biisoquinolines (Scheme ). On the basis of preceding studies, sequential synthesis is the convenient approach for generating bisheterocycles. Nonetheless, the easiest way is a one-pot approach.…”