Conformationally restricted functionalized heteroaromatics: a direct access to novel indoloindoles via Pd-mediated reaction

Abstract

A new, versatile and direct Pd-mediated method involving intramolecular cyclization of N-(2-iodoaryl)-N-(1-alkyl-1H-indol-2-yl)alkane/arene/heteroarene sulfonamide has been developed leading to a diverse and unique class of indolo[2,3-b]indoles for the potential inhibition of sirtuins.

Palladium-Catalyzed Amination of N-Free 2-Chloro-7-azaindole

“…Pd-catalyzed cross-coupling of primary and secondary amines with halo-7-azaindoles have been reported but were restricted on the pyridine ring . Alternatively on position 2, only metal-free iodine-promoted amination using a N -sulfonyl amine or direct C–H azolation were successfully achieved, but in each case with a very limited scope (one amine) (Scheme ). Therefore, a more general and suitable method is needed to give access to original aminated 7-azaindoles, which are also important scaffolds in medicinal chemistry (Figure ).…”

KOtBu-Mediated Aerobic Transition-Metal-Free Regioselective β-Arylation of Indoles: Synthesis of β-(2-/4-Nitroaryl)-indoles

“…Aryl-indoles and their analogues constitute a large number of biologically important pharmaceuticals, fragrances, agrochemicals, conducting polymers, and ligands. , As a result, several methodologies have been developed to construct aryl-indoles (Scheme ). − Transition-metal-catalyzed coupling of aryl halides with indoles under heating conditions is one of the conventional routes to access aryl-indoles. , Apart from aryl halides, benign coupling partners such as boronic acids, sodium sulfinates, acids, silanes, phenylhydrazine hydrate, and [Ph-I-Ph]BF 4 have been used for the synthesis of α-/β-aryl-indoles under palladium- or copper-catalyzed methodologies (eq 1). , Transition-metal-catalyzed approaches to the direct C-(β)-arylation of protected indoles using arenes have also been reported under harsh reaction conditions (eq 2) . Nonetheless, these reactions provide a mixture of α-, β-, and α,β-diaryl-indoles and are only suitable for the nonsubstituted and symmetrically substituted arenes, as regioselective coupling of arenes has not been achieved .…”

Unified Strategy to Access 6H‐Benzofuro[2,3‐b]indoles and 5,6‐Dihydroindolo[2,3‐b]indoles via UV Light‐Mediated Diradical Cyclization

“…Indole derivatives are one of the most important nitrogen‐containing heterocycles with wide‐spectrum bioactivities and diverse structures . Among them, 6 H ‐ benzofuro[2,3‐ b ]indoles and 5,6‐dihydroindolo[2,3‐ b ]indoles, two intriguing classes of heterocycle‐fused indoles, have attracted tremendous attention owing to their wide applications in functional materials (such as OLED), pharmaceutical/medicinal chemistry and other scientific fields. Especially, C10b functionalized 5a,10b‐dihydro‐6 H ‐benzofuro[2,3‐ b ]indoles widely distributed in quite a number of natural products such as diazonamide A and azonazine (Figure ), had raised broad interest from organic community, and a variety of efficient approaches to build this framework were developed, including intramolecular [3+2] annulation, intramolecular electrosynthesis, and iminium‐catalyzed cascade process, among others .…”

“…In contrast, only a few methods for the construction of 6 H ‐ benzofuro[2,3‐ b ]indoles and 5,6‐dihydroindolo[2,3‐ b ]indoles have been reported. The major synthetic approaches to 5,6‐dihydroindolo[2,3‐ b ]indoles include two classes: (i) Pd‐mediated C−I/C−H or oxidative C−H/C−H coupling reaction (Scheme , path (a)), (ii) electrophilic amination of arene C−H bond, Cadogan cyclization, and iodine‐mediated cyclization (path b) . As for 6 H ‐ benzofuro[2,3‐ b ]indoles, there are only two synthetic routes via copper‐mediated coupling reaction or oxidative cycloamination reaction in literature.…”