The pyrrolate ion (5) is shown to produce N, N′‐dipyrrolyl methane (4) when reacted with dichloromethane under conditions of weak counter‐ion association. 1‐Azoniafulvene ion (13) is suggested to be the key intermediate in this reaction. N, N′‐Dipyrrolyl methane (4) undergoes intramolecular oxidative coupling when treated with butyllithium and Cu(II)chloride, yielding the novel ring system of dipyrrolo [1,2c: 2′, 1′e]‐2 H‐imidazole (3). The latter upon reaction with methyl lithium forms the Hückel‐aromatic anion 2. Solutions of the lithium salt are stable for several days. Reaction of the dianion of 2,2′‐bipyrrole (11) with dichloro‐methane does not produce 3, but a pyrrolophane‐type dimer (12) having its two anticoplanar N, N′‐bipyrrolediyl subunits arranged in a double layer and joined by a methylene group on each side.
Summary
4-Azapentalenyl anion (4)is shown to react with dichloromethane/butyl lithium in two fundamentally different ways depending on whether diethyl ether or tetrahydrofuran is chosen as solvent. ln the first case a tetracyclic valence isomer of indolizine, i.e. pyrrolo-3-azabenzvalene (6) is formed together with indolizine (8) itself. In THF however, a pyrrylbutenyne (9), isomeric with the products mentioned above is obtained in a stereospecific reaction. Once again the appearance of indolizine (8) accompanies the reaction. Mechanistic implications, based on the finding that the heterovalene 6 is not a precursor of the pyrrylbutenyne 9, are discussed.Einleitung. -
SummaryThe pyrrolate ion (5) is shown to produce N, N'-dipyrrolyl methane (4) when reacted with dichloromethane under conditions of weak counter-ion association. 1 -Azoniafulvene ion (13) is suggested to be the key intermediate in this reaction. N , N'-Dipyrrolyl methane (4) undergoes intramolecular oxidative coupling when treated with butyllithium and Cu (II)chloride, yielding the novel ring system of dipyrrolo [ 1,2 c: 2', l'el-2 H-imidazole (3). The latter upon reaction with methyl lithium forms the Hiickel-aromatic anion 2. Solutions of the lithium salt are stable for several days. Reaction of the dianion of 2,2'-bipyrrole (11) with dichloromethane does not produce 3, but a pyrrolophane-type dimer (12) having its two anticoplanar N , N'-bipyrrolediyl subunits arranged in a double layer and joined by a methylene group on each side.Recent publications from our laboratory have discussed the reactions of carboaromatic anions with chlorocarbene [ 11 [2]. Following our studies of 4-azapentalenyl lithium (1) [3] [4], access to new simple heteroaromatic anions was desired. Our interest focused on dipyrrolo-2 H-imidazolyl lithium (2). Surprisingly, this simple analogue of the fluorenyl system as well as its parent compound, dipyrrolo-1,2 c : 2', 1 'el-2 H-imidazole (3) or any derivatives thereof, were completely unknown. It is the purpose of this communication to show how the target anion (2) and other novel heterocyclic systems can be constructed in a few straightforward steps starting from pyrrole.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.