Heterocyclic betaines. Aza analogs of sesquifulvalene. 2. Azolium azolate inner salts: synthesis, reactivity, and structure of a 1:1 adduct with dimethyl acetylenedicarboxylate
摘要:
Reaction of an activated 2-chloroazole with several N-alkylazoles afforded the N-azolylazolium salts, deprotonation of which results in a series of the title mesomeric betaines 7 and 8. Their reactivity toward electrophiles and dipolarophiles under mild conditions reflects the highly dipolar structures of 7 and 8. The thermal stability and dequaternization reactions of some of their corresponding N-azolylimidazolium and -pyrazolium salts have also been studied.
A facile entry into the almost unknown azolium azolate inner salts is described, and the structure of these highlydipolar compounds is well reflected by their spectroscopic properties and reactivity towards electrophiles (MeI) and dipolarophiles (DMAD) under mild conditions.