The Reaction of ω-Ethoxyalkyl Bromides with Silver(I) Cyanide and Nitrite. The Participation of an Oxonium Ion

The reaction of ω-ethoxyalkyl bromides (Cn: n=2–5) with silver(I) cyanide or nitrite in less polar solvents to give the corresponding isocyanide or a mixture of the corresponding alkyl nitrite and nitroalkane respectively, proceeded with ease only when n=4. In the latter reaction, the ratios of O- and N-attack (O/N) were 16–18/ 82–84 and 31–46/54–69 when n\eweq4 and n=4 respectively. The facile reaction in both cases when n=4 and the increasing O-attack in the case of silver(I) nitrite may suggest that the reaction proceeds through the initial formation of a five-membered oxonium ion, the O-ethyltetrahydrofuranium ion, and a subsequent attack by CN− and NO2− or their silver(I) bromide complex.