... Using this compound as starting material, we succeeded in the preparation of eighteen new dipyrrolylethenes. ... on precoated aluminium sheets (60 F 254 ) with a 0.2 mm thickness (Aldrich Chemical Co ... with a cold (−30 °C) mixture of HCl–EtOH–THF (1 ∶ 2 ∶ 2 in volume, 1 mL ...