Synthesis and Molluscicidal Activity of New Chromene and Pyrano[2,3‐ c ]pyrazole Derivatives

The chromene derivative 4 reacts with acetic anhydride, phenylisothiocyanate and ethyl orthoformate to afford the N ‐acetyl derivative 6 , the chromenopyrimidine 8 and the formimidate 9 , respectively. 2‐(1 H ‐Indol‐3‐ylmethylene)‐malononitrile 10b reacts with 1,3‐cyclohexanedione and dimedone 11a , b to afford the 4(3‐indolyl)‐chromene derivatives 12a , b respectively, and with the pyrazolone derivatives 13a–d to afford the arylidene exchange derivatives 14a–c and the pyranopyrazole derivative 15 , respectively. The arylidene derivatives 10a , b react also with indane‐1,3‐dione 16 to afford the arylidene exchange derivatives 18a , b . The molluscicidal activity of the synthesized compounds towards Biomphalaria alexandrina snails, the intermediate host of Schistosoma mansoni , was investigated and most of them showed weak to moderate activity.