Flow Photochemistry of Azosulfones: Application of “Sunflow” Reactors

Abstract

Arylazo sulfones have been established as photoactive precursors in visible‐light photoreactions without any additional catalysts. The arylation of various (hetero) aromatic substrates and isonitriles was carried in a simple solar microcapillary reactor in three different geographical locations (Germany, Italy and Brazil). High conversion of the starting substrates as well as short reaction times were observed.

Metal-free synthesis of biarenes via photoextrusion in di(tri)aryl phosphates

“…Scheme 1a) followed by the reaction of the thus formed aryl cation with an aromatic substrate. In an alternative approach, aryl radicals may be generated under photoredox catalysis conditions (mostly from arene diazonium salts or aryl iodides) [30,31] or by the direct photolysis of arylazo sulfones [38][39][40] and employed for the desired arylations. These reactions have the advantage of being applied to non-functionalized arenes but have the drawback to require a large excess of the nucleophilic reagent (the arene Ar-H) in up to 10-20-fold amount.…”

Solar Photochemistry in Flow

“…a sunflow built in Mainz, Germany, b sunflow built in Ribeirão Preto, Brazil, c sunflow built in Pavia, Italy. Reprinted with permission from [39]. Copyright 2016 John Wiley and Sons…”

“…The sunflow reactor has also been applied by the same authors to the arylation of isonitriles and heteroaromatic substrates via photolysis of azosulfones [39].…”

Solar Photochemistry in Flow

“…While benzophenone and phenanthrene only marginally absorb in the UV-A, the strong absorption of rose bengal in the visible ( max = 558 nm ) allows for faster reaction apparent kinetics with lower photocatalyst loading. The sunflow reactor has also been applied by the same authors to the arylation of isonitriles and heteroaromatic substrates via photolysis of azosulfones [39].…”