DURGA PRASAD HARI, THEA HERING, AND BURKHARD KÖNIG*
*Corresponding author
Universität Regensburg, Institut für Organische Chemie, Universitätsstraße 31, D-93053 Regensburg, Germany

Abstract

The application of aryl radicals in organic synthesis is challenging, but very useful. Recently their generation from aryl diazonium salts via visible light photocatalysis has been developed as an efficient alternative to established methods in chemical synthesis. We summarize here our contributions to this fast developing area of research.

INTRODUCTION

Aryl diazonium salts are an important class of intermediates and have found - many applications in organic synthesis (1). In addition, aryl diazonium salts serve as an alternative to aryl halides, which have been widely used in transition metal mediated cross coupling reactions for carbon-carbon and carbon-hetero bond formation (2). The electrophilic nature of diazonium salts arises from N2 being a good leaving group, which does not interfere with the reaction mixture and allows the use of ambient reaction conditions. The chemistry of diazonium salts has been studied for long starting around 1858. Several name reactions associated with aryl diazonium salts including the Sandmeyer reaction (1884), the Pschorr cyclization (1896), the Gomberg–Bachmann reaction (1924), and the Meerwein arylation (1939) were developed (3).
Meerwein first reported the arylation of coumarin, cinnamic acid, and acrylic acid with aryl diazonium salts catalyzed by copper (II) salts (4) ...