N,N-dialkoxyamides 1c, a virtually unstudied member of the new class of anomeric amides, amides bearing two electronegative atoms at nitrogen, have been synthesised in useful yields directly from hydroxamic esters using phenyliodine(III)bis(trifluoroacetate) (PIFA). Infrared carbonyl stretch frequencies and carbonyl (13)C NMR properties have been reported, which support strong inhibition of amide resonance in these amides. Their thermal decomposition reactions in mesitylene at 155 °C proceed by homolysis to form alkoxyamidyl and alkoxyl free radicals in preference to HERON rearrangements to esters. The reactions follow first-order kinetics and for a series of N,N-dimethoxy-4-substituted benzamides, activation energies of 125-135 kJ mol(-1) have been determined together with weakly negative entropies of activation.

The HERON reaction has been observed in the thermal decompositions of N-acyloxy-N-alkoxyamides 1b, members of the class of anomeric amides. The N,N-bisoxo-substitution results in reduced amide resonance and this, combined with an nO–σ*NOAcyl anomeric destabilization of the N–OAcyl bond, results in their intramolecular rearrangement to anhydrides 42 and alkoxynitrenes 43 in competition with homolysis of the N–OAcyl bond to alkoxyamidyls 51. The primary HERON product alkoxynitrenes are scavenged by oxygen, giving a nitrate ester, in competition with a rearrangement to nitriles and dimerization to hyponitrites, leading, under the conditions, to alcohols and aldehydes. Persistent alkoxyamidyls most likely form a 1,3-diradical in a solvent-cage reaction, which cyclizes to 3,5-disubstituted-(5H)-1,4,2-dioxazoles 47. Substituent effects support this competition reaction.