A Photoredox‐Induced Stereoselective Dearomative Radical (4+2)‐Cyclization/1,4‐Addition Cascade for the Synthesis of Highly Functionalized Hexahydro‐1H‐carbazoles

Abstract

A stereoselective synthesis of functionalized hexahydrocarbazoles was developed based on an unprecedented photoredox-induced dearomative radical (4+2)-cyclization/1,4-addition cascade between 3-(2-iodoethyl)indoles and acceptor-substituted alkenes. The title reaction simultaneously generates three C-C bonds and one C-H bond, along with three contiguous stereogenic centers. The hexahydro-1H-carbazole products are highly valuable intermediates for the synthesis of novel antibiotics, as well as unnatural ring homologues of polycyclic indoline alkaloids.

Redox and photocatalytic properties of a NiII complex with a macrocyclic biquinazoline (Mabiq) ligand

“…The radical cyclization of the N -(ω-bromoalkyl)-substituted indole 3 was chosen as a test reaction. 14 The reaction had been previously studied by the Stephenson group and was found to produce mainly product 4 by C–C bond formation under optimized conditions. 15 Under non-optimized conditions, hydro-de-bromination was a competing side reaction and varying product ratios of 4 and 5 were observed.…”

Aminoalkyl radicals as halogen-atom transfer agents for activation of alkyl and aryl halides

“…However, photoredox activation has thus far rarely extended to organic halides, one of the largest class of building blocks available to organic chemists. The current synthetic gap is especially evident in the case of unactivated alkyl halides, where only dehalogenation and intramolecular cyclization of iodides have been reported (7)(8)(9)(10). The difficulties in engaging these feedstocks in redox chemistry arise from their highly negative reduction potentials (Ered < -2 V vs SCE for unactivated alkyl and aryl iodides), which in turn necessitate the use of strongly reducing systems (11,12) (Fig.…”

“…After optimization, we achieved efficient deuteration of primary, secondary and tertiary alkyl iodides in nearly quantitively yields (5)(6)(7)(8)(9)(10)(11)(12). The mild reaction conditions tolerated multiple functional groups showcasing the strong chemoselectivity of this XAT approach.…”

A comprehensive mechanistic study on the visible-light photocatalytic reductive dehalogenation of haloaromatics mediated by Ru(bpy)3Cl2

“…During the past decades, visible-light photoredox catalysis has been in the focus of many investigations due to its efficiency, versatility and potential applications, which range from environmental remediation [1][2][3][4][5][6] to synthetic chemistry. [7][8][9][10][11][12] In this context, tris(2,2′-bipyridyl)ruthenium(II) chloride, (Ru(bpy)3Cl2), has been widely used as transition metal based photocatalyst for a great number of chemical processes. [13][14][15][16][17][18][19][20][21][22] However, the precise role of Ru(bpy)3 2+ in such photochemical processes is often unclear, since elucidation of the operating oxidative or reductive quenching cycle is often forgotten, in spite of its importance to optimize selection of reactants.…”