Dual Catalysis in DominoN-Benzylation/Intramolecular C-H Arylation: Regio- and Chemoselective Synthesis of Annelated Nitrogen Heterocycles

Recent advances in the synthesis of pyrrolo[1,2-a]indoles and their derivatives

The pyrrolo[1,2-a]indole unit is a privileged heterocycle found in numerous natural products and has been shown to exhibit diverse pharmacological properties. Thus, recent years have witnessed immense interest from the synthesis community on the synthesis of this scaffold. In light of the ever-increasing demand for pyrrolo[1,2-a]indoles in drug discovery, this review provides an overview of recent synthesis methods for the preparation of pyrrolo[1,2-a]indoles and their derivatives. The mechanistic pathway and stereo-electronic factors affecting the yield and selectivity of the product are briefly explained. Furthermore, we have attempted to demonstrate the utility of the developed methods in the synthesis of bioactive molecules and natural products, wherever offered.

A three-component iodine-catalyzed oxidative coupling reaction: a heterodifunctionalization of 3-methylindoles

A metal-free method for the synthesis of heterodifunctional indole derivatives is developed through TBHP/KI-mediated oxidative coupling. The reaction constructs C-O and C-C bonds in succession with the help of tert-butyl peroxy radicals generated by the TBHP/KI catalytic system, enabling the direct realization of the heterodifunctionalization of indole in one pot. The product of this reaction is a novel heterodifunctional compound. This work might provide a new effective method for the synthesis of polycyclic indole compounds.

Highly selective Diels-Alder and Heck arylation reactions in a divergent synthesis of isoindolo- and pyrrolo-fused polycyclic indoles from 2-formylpyrrole

A highly regio-, chemo- and stereoselective divergent synthesis of isoindolo- and pyrrolo-fused polycyclic indoles is herein described, starting from 2-formylpyrrole and employing Diels-Alder and Heck arylation reactions. 3-(N-Benzyl-2-pyrrolyl)acrylates and 4-(pyrrol-2-yl)butenones underwent a highly endo-Diels-Alder cycloaddition with maleimides to furnish octahydropyrrolo[3,4-e]indoles, which served as precursors in the regioselective synthesis of aza-polycyclic skeletons via an intramolecular Heck arylation reaction. Through the latter reaction, the 3-(N-benzyl-2-pyrrolyl)acrylates give rise to 3-(pyrrolo[2,1-a]isoindol-3-yl)acrylates. A further oxidative aromatization of the polycyclic intermediates provides the corresponding polycyclic pyrrolo-isoindoles and isoindolo-pyrrolo-indoles. A theoretical study on the stereoselective Diels-Alder reactions, carried out by calculating the endo/exo transition states, revealed the assistance of non-covalent interactions in governing the endo stereocontrol.

Palladium-catalysed regioselective N-arylation of anthranilamides: a tandem route for dibenzodiazepinone synthesis

A palladium-catalyzed tandem reaction of 2-aminobenzamide and 1,2-dihaloarenes for the synthesis of dibenzodiazepinone via double N-arylations (inter and intra-molecular) has been achieved.

Methods for the synthesis of annulated pyrroles via cyclisation strategies

In this report, we review the methods that have been employed to synthesise annulated pyrroles.

Ruthenium(ii)-catalyzed C–H alkenylation/annulation cascade for the rapid synthesis of benzoimidazoisoindoles

A one pot synthesis of benzimidazole-fused isoindoles from 2-arylbenzimidazole and conjugated alkenes has been explored. The strategy involved the ruthenium-catalyzed formation of C–C and C–N bonds and a new five-membered ring.

Implications of dynamic imine chemistry for the sustainable synthesis of nitrogen heterocycles via transimination followed by intramolecular cyclisation

An application of dynamic imine chemistry to the sustainable synthesis of N-heterocycles from N-aryl benzylamines or imines and ortho-substituted anilines is described.

A Highly Regioselective C-3 Benzylation Reaction of Indoles with Alcohols Catalysed by an N-Heterocyclic Carbene

The direct C-3 alkylation of indoles with primary and secondary alcohols through the combination of KOH and an N-heterocyclic carbene is described. The KOH/NHC-catalysed system can give desired C-3 alkylated indoles with high selectivity in moderate to excellent yields. Moreover, this process has obvious advantages such as high atom economy and the absence of a metal source.