Synthesis and Characterization of Acridinium Dyes for Photoredox Catalysis

Abstract

Photoredox catalysis is a rapidly evolving platform for synthetic methods development. The prominent use of acridinium salts as a sustainable option for photoredox catalysts has driven the development of more robust and synthetically useful versions based on this scaffold. However, more complicated syntheses, increased cost, and limited commercial availability have hindered the adoption of these catalysts by the greater synthetic community. By utilizing the direct conversion of a xanthylium salt into the corresponding acridinium as the key transformation, we present an efficient and scalable preparation of the most synthetically useful acridinium reported to date. This divergent strategy also enabled the preparation of a suite of novel acridinium dyes, allowing for a systematic investigation of substitution effects on their photophysical properties.

Photocatalysis with organic dyes: facile access to reactive intermediates for synthesis

“…In the last years, several classes of organic dyes, such as acridiniums (OD1-4), cyanoarenes (OD5-8), diaryl ketones (OD9/ 10), flavins (OD11/12), xanthenes (OD13-15), thiazines (OD16/17) and various other dyes, such as OD18-21, have been exploited (Figure 1), and the field of organic photocatalysis has been extensively covered by various reviews [16,[19][20][21][22][23][24][25]. Most of these reports are organized according to the structural features of the dye and/or their applications in synthetic chemistry.…”

Emerging Organic Photoredox Catalysts for Organic Transformations

“…Acridiniums can also be synthesized through direct conversion of the corresponding xanthylium salt, as reported by Nicewicz and co‐workers . Xanthylium salt was prepared from double directed ortho‐metalation (D o M) with lithium of biaryl ether, followed by the coupling of esters (Scheme b), which therefore rendered a facile and scalable method to separately modulate the acridinium core, C9‐ and N ‐substituents.…”

Design and application of aminoacridinium organophotoredox catalysts

“…16 Recently, Nicewicz and co-workers designed an efficient synthesis of acridinium photocatalysts starting from xanthylium salts. 17 The rapid assembly of a xanthylium dye was thereby combined with a condensation reaction with an aniline to give the corresponding acridinium salt 1.…”