Electron transfer in aromatic substitution

Kim and Bunnett in 1970 made unexpected observations of reactions occurring by an electron transfer chain mechanism in aromatic systems. The selective formation of 60 showed that benzyne intermediates were not formed, and the mechanism of equations (90) and (91) analogous to that found in aliphatic systems (equations 88, 89) was proposed. This process differs in being a chain reaction and not a process in which the product forming step is not a radical-radical combination. 

The utilization of electrochemistry for electron transfer in organic reactions dates back to Kolbe (equation 2), and continues to be a subject of great The respective roles of stepwise and concerted dissociative 

The Utilization of free radical reactions in synthesis, particularly for the formation of carbon-carbon bonds, was given great impetus by initial studies 

Stereocontrol of free radical reactions has proven to be possible, as in the example shown (equation 95), and is widely exploited. The use of chiral auxiliaries as illustrated has proved to have a wide application. 

The inclusion of stable free radicals such as TEMPO (18, TO ) in free radical polymerizations leads to precise control of chain length by restricting the number of polymerizing chains (equation 96). This process is known as nitroxyl radical mediated polymerization (NRMP). 

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Radical ions from arenes Birch reduction and arene oxidation Electron transfer in aliphatic substitution 38 Electron transfer in aromatic substitution 38 Electrochemical electron transfer 39... 

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