Abstract
4, 5-Benzotropone reacted with malononitrile in acetic anhydride or in ethanol-piperidine to afford 8, 8-dicyano-3, 4-benzoheptafulvene (6a). On the other hand, 2, 3-benzotropone reacted with malononitrile in acetic anhydride to afford 8, 8-dicyano-1, 2-benzoheptafulvene (8a) and 6-cyano-7-amino-3, 4-benzobicyclo[3, 2, 2]nona-3, 5, 8-trien-2-one (9a). The reaction mechanism revealed that 8a was afforded not only by Knoevenagel reaction but also by Michael addition at 4-position of 2, 3-benzotropone.
