Anodic Addition via Radical Cations as Intermediates

This mode of anodic addition involves oxidation of the substrate RH, an olefin or aromatic compound, to a radical cation, in contrast to the oxidations of the reagent Nu , depicted in the preceding sections a) and b). The adduct is formed in a EC ECj j- sequence (Eq. (119))  

In this way furanes form 2,5-dialkoxy-2,5-dihydrofuranes in high yields on electrolysis in R 0H/NH4Br (Eq. (120) )  

With suitable substituents intramolecular alkoxylation to spiroketals can be achieved (Eq. (121) ) 215 For details on alkoxylation of furans thd reader is referred to extensive Tables in Ref. 10  

Rosse al. 10S obtained a 1 1 mixture of cis- and trans-2,5-dimethyl-2,5-di-methoxy-2,5-dihydrofurane (60) from 2,5-dimetliylfurane both by electrochemical and chemical oxidation. Besides 60 minor amounts of 5,5 -bis (2-methoxy-2-methyl-2,5 -dihydrofurane) (61), the dimer of the intermediate radical cation, were isolated. 2-Cyano-5-metlioxy-2,5-dimethyl-2,5-dihydrofurane was obtained on electrolysis of 2,5-dimethylfurane in methanol-NaCN 276  

Analogous alkoxy-adducts are obtained with alkoxylated benzenes or pyri-dines (Table 9)89. 

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