C–H Bond Functionalization of 1,4‐Benzoquinone by Silver‐Mediated Regioselective Phosphination and Amination Reactions

Abstract

The one‐pot synthesis of 2,5‐bis(diarylphosphoryl)‐3,6‐bis(arylamino)cyclohexa‐2,5‐diene‐1,4‐diones has been achieved by AgI‐mediated full C–H functionalization of 1,4‐benzoquinone (BQ) through regioselective dual phosphination and amination reactions. BQ, diarylphosphine oxides [SPOs, Ar2PH(=O)], and imines reacted to give the products under mild conditions. 1,4‐Naphthoquinone (NQ) could also be used instead of BQ. When aniline was used instead of the corresponding imine, a lower yield of the desired product was obtained. In the absence of Ag2CO3, hydrophosphinylation of the imine by the SPO occurred as a competitive side‐reaction. AgI plays versatile roles in this reaction, as a mediator for facilitating the consecutive additions of Ar2P(=O)– and aniline to the related β‐carbon atoms of BQ, as an oxidant of hydroquinone (HQ) intermediates to form the substituted BQ counterpart, and as an inhibitor of the hydrophosphinylation side‐reaction of the imine by the SPO. The X‐ray crystal structures of several new products have been determined. A reaction mechanism is also proposed based on the experimental results.

Palladium-Catalyzed C-H Functionalization of Amido-Substitued 1,4-Napthoquinone in the Presence of Amines toward the Formation of Pyrroles and Imidazoles

“…In recent years, the study of carbon‐hydrogen bond activation (C−H activation) on inert sp 2 or sp 3 carbon and followed by functionalization to various substituents has stimulated great interests both from synthetic and theoretical realms . Our previous work had demonstrated that the C−H functionalization of benzoquinone framework could be achieved via replacing protons by variable numbers of amino‐ and phosphino‐groups . In order to explore the chemical reactivity of the C−H bonds on benzoquinone to a greater extent, further research by employing amido‐substituted 1,4‐naphthoquinone as a model in C−H activation was pursued.…”

The Different Facets of Metal‐Catalyzed C−H Functionalization Involving Quinone Compounds

“…An interesting Ag‐mediated phosphination/amination reaction of quinones was reported by Hong and co‐workers in 2017 (Scheme 62). [98,99] During an attempted phosphination of diphenylmethanimine using Ag(I), Pd(OAc) 2 and benzoquinone as a co‐catalyst, the diarylphosphine oxide and aniline adduct of benzoquinone was instead isolated. After extensive probing of the reaction conditions, some conclusions were made regarding the mechanism of this transformation.…”

Recent Advances in Direct Functionalization of Quinones

“…Recently, Hong et al reported a one‐pot synthesis of 2,5‐bis(diarylphosphoryl)‐3,6‐bis(arylamino)cyclohexa‐2,5‐diene‐1,4‐diones 48 by silver‐mediated full C–H functionalization of 1,4‐benzoquinone through regioselective dual phosphination and amination reactions (Scheme ) . 1,4‐Naphthoquinone could also be used instead of 1,4‐benzoquinone.…”