On the Use of N, N′‐Dipyrrolylmethane in Heterocyclic Synthesis. Dipyrrolo [1,2c:2′, 1′e]‐2 H‐imidazole and its Aromatic Anion

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.