Mesoionische 4nπ-Heterocyclen, I Mesoionische 4π-Fünfringheterocyclen und 8π-Heteropentalene. Entwicklung der Systeme und Untersuchungen am 1-Oxo-lH-pyrazolo [1.2-a] pyrazol-4-ium-3-olat-Typ / Mesoionic 4nπ-Heterocycles, I Mesoionic 4π Five-Membered Heterocycles and 8 π-Heteropentalenes. Development of the Systems and Investigations on the 1-Oxo-1H-pyrazolo[1,2-a]pyrazol-4-ium-3-olate Type

Abstract

Abstract 4n π-Mesoionic heterocycles are -with one exception -a hitherto unknown class of compounds. In this paper the possible 4 π-five-membered mesoionic heterocycles, their ring anellated derivatives and the corresponding heteropentalenes are derived. Reactions of the 1-oxo-1H-pyrazolo[1,2-a]pyrazol-4-ium-3-olate system with tetrachloro-o-benzo-quinone are described.