Intermolecular thermal reaction of arylnitrenes with furans

4-Methoxy-, 4-chloro-, and 4-nitro-phenylnitrenes have been thermally generated by decomposition of the corresponding aryl azides in the presence of furan and a series of 2-substituted and 2, 5-disubstituted furans. 4-Nitrophenylnitrene has been shown to be capable of undergoing electrophilic addition to the furan ring both at the α- and β-position, whereas only evidence of α-attack has been provided by 4-chlorophenylnitrene. On the other hand, no evidence of electrophilic attack has been obtained with 4-methoxyphenylnitrene, which affords only products ascribable to the triplet nitrene. The formation of a number of products ultimately resulting from nitrene attack at the α-position of the furan ring followed by a ring-opening process and the general occurrence of 1-(4-nitrophenyl) -and 1-(4-chlorophenyl) -1,2,3-triazole from thermolysis of 4-nitro- or 4-chloro-phenyl azide in the presence of the furans examined is discussed.