Radicals Containing Oxazole and Thiazole Rings

Anion-radicals generated from oxazole and isoxazole in an argon matrix were shown, like their counterpart from furan, to have undergone ring scission. Consistent with this, various attempts to reduce isoxazoles polarographically in both protic and aprotic media have also resulted in the loss of ring integrity, and indeed the reduction process has always involved two electrons. However, electrochemical reduction of 

5-diaryloxazoles has been shown to give anion-radicals as the initial product, although the presence of proton sources may change 

Goyal and R. Jain, J. Electroanal. Chem. Interfacial Electrochem. 79,407 (1977). 

The anion-radicals from 2,5-diphenyloxazole and similar substances are sufficiently persistent for use in various electrochemiluminescent systems. °  

Thiazole gives a transient radical in aqueous solution upon pulse radiolysis. The radical formed under neutral conditions is the 3-hydrothiazolyl radical (201) for which electronic absorption spectra, acid-base characteristics, and second-order decay kinetics were measured. A derivative of this, the radical from thiamine (vitamin Bi) (202) was also characterized. A role is implied for related radicals (e.g., 203) during the electrochemical dimerization reported for benzothiazolium salts.  

Radicals Containing a Five-Membered Heterocycle 1. Radicals Containing Oxazole and Thiazole Rings 

Various thiazole anion-radicals have been characterized by ESR. Tordo and co-workers have generated several nitrothiazole anion radicals (e.g., 204 and 205) by reduction of the precursors with glucose in methanol containing 

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