Synthesis of isomeric benzodipyrrolenines and their derivatives
The Fischer reaction was used to synthesize 2,3,3,5,5,6-hexamethyl-3H,5H-benzo[1,2-b∶5,4-b′]dipyrrole and 2,3,3,7,8,8-hexamethyl-3H,8H-benzo[1,2-b∶3,4-b′]dipyrrole from the dihydrazone obtained by the action of methyl isopropyl ketone on m-phenylenedihydrazine. Centrosymmetrical 2,3,3,6,7,7-hexamethyl-3H,7H-benzo[1,2-b∶4,5-b′]dipyrrole was synthesized from p-phenylenediamine and methyl bromoisopropyl ketone. Mono- and diquaternary salts were obtained from the new bases. The diquaternary salts were converted to bismethylene bases.