Visible-Light-Induced Organophotoredox-Catalyzed Phosphonylation of 2H-Indazoles with Diphenylphosphine Oxide

Abstract

A metal-free visible-light-induced phosphonylation of 2H-indazoles with diphenylphosphine oxide has been developed using rose bengal as an organophotoredox catalyst under ambient air at room temperature. A library of diphenyl(2phenyl-2H-indazol-3-yl)phosphine oxide with broad functionalities has been synthesized in high yields. The experimental result suggests the radical pathway of the reaction.

Visible light-mediated C P bond formation reactions

“…In proposed mechanism, the photogenerated radical cation 60 and 61 are recognized as the key intermediates. Since the above elegant discoveries, visible light-promoted C (sp 2 )AH phosphorylation of other heterocyclic ring structures, including coumarins [60], quinoxalin-2(1H)-ones [61] and 2Hindazoles [62] was sequentially disclosed by different research groups.…”

Recent Advances in the Construction of Phosphorus‐Substituted Heterocycles, 2009–2019

“…Phosphorus‐substituted 2 H ‐indazoles have gained great attention in the field of medicinal and organic chemistry. A metal‐free synthesis of such compounds via visible light‐mediated phosphonylation of 2 H ‐indazoles with diarylphosphine oxides has been disclosed by the group of Hajra . The employment of 3 mol% of Rose Bengal (RB) as an organophotoredox catalyst together with 35 W blue LED facilitated the C( sp 2 )−P bond formation with good generality for 2 H ‐indazoles 99 bearing electron‐donating or electron‐withdrawing groups to afford a variety of phosphinoylated indazoles 100 in high to excellent yields (Scheme ).…”

Direct Catalytic Functionalization of Indazole Derivatives

“…Our group has developed several functionalization methods for indazole derivatives. [63][64][65][66][67][68] indazole, herein, we first report a brief review on direct functionalizations including arylation, alkylation, acylation, alkenylation, alkynylation, trifluoromethylation, selenylation, nitration, cyanation, bromination, carbonylation and oxyalkylation of indazole derivatives. This article covers most of the related papers published in the last 20 years.…”