Evidence against the Intramolecular Cyclization of o-Azidobenzenediazonium Ions

Article abstract of DOI:10.1021/jo01314a002

The question regarding the possibility that o-azidobenzenediazonium ions might cyclize to give pentaaza analogues of benzotropylium ions was investigated experimentally.Samples of 4-chloro-2-azidobenzenediazonium ion (5) and 5-chloro-2-azidobenzenediazonium ion (6) were prepared separately by diazotization of the corresponding chloroazidoanilines and were treated subsequently with cuprous chloride.From each of these Sandmeyer reactions only the unrearranged product was obtained: 2,5-dichloroazidobenzene from 5 and 2,4-dichloroazidobenzene from 6.The absence of detectable amounts of crossover products in both reactions (within the limits of detection of about 5-10percent) demonstrates that the conversions of ions 5 and 6 to the hypothetical benzotropylium-like cyclized ion 7 are not kinetically significant processes.The failure of this type of cyclization is attributed to a high energy barrier for the reorganization of the 12?-electron system in ions 5 and 6 to the 10?-electron system in ion 7.