Reaction Pathways for Arylcarbamoyl Radicals and the Cyclization of o-Substituted Phenylcarbamoyl Radicals

Article abstract of DOI:10.1039/P19810003164

N-Arylcarbamoyl radicals generated from N-arylformamides with di-t-butyl peroxide (Bu^tOOBu^t) in chlorobenzene at 110 deg C give rise to a series of reactions depending on the nature and the position of the substituent in the aromatic ring.When the aryl group is phenyl or p-chlorophenyl the following reactions on carbamoyl radicals occur: (i) loss of hydrogen with formation of aryl isocyanates, whereas the loss of carbon monoxide leads to arylamines via arylaminyl radicals; (ii) dimerization to NN'-diaryloxamides; (iii) aromatic substitution on chlorobenzene leading to N-arylbenzamides (ipso-substitution) and N-arylchlorobenzamides.The isocyanates trapped by t-butyl alcohol and arylamines give t-butyl N-arylcarbamates and NN'-diarylureas.With o-substituted N-phenylformamides intramolecular cyclization is observed as well; in fact, the N-(o-cyanophenyl)formamide affords isatin via addition of the carbamoyl radical to the cyano-group while the N-<(o-phenylthio)phenyl>formamide gives 2-benzothiazolone and phenyl radicals through an S_Hi reaction on the sulphur atom; finally 2-formamidobiphenyls furnish phenanthridones in very high yields.

Full text of DOI:10.1039/P19810003164

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