Synthesis of donor‐substituted 2‐benzopyrans, isoquinolines, and cinnolines with acetal structure

At −105°C the aryllithium intermediate 7 , which was generated by treatment of the donor‐substituted bromo acetal 6 with n ‐butyllithium, was trapped with aromatic and aliphatic aldehydes, with paraformaldehyde, with a ketone, an amide, an imine, and an azo compound to yield the hydroxy acetals 9a–c and 18 , the homophthalaldehyde derivative 8 , the amino acetal 24 and the hydrazino acetal 28. The acid‐catalyzed ring closure of the hydroxy acetals 9a–c and 18 , the amino acetal 24 , and the hydrazino acetal 28 provided the 2‐benzopyrans 10a–c , 19 and 20 , the isoquinoline 26 , and the cinnolines 29 and 30 , respectively. Hydrogenolysis (H 2 , Pd/C) of the benzyl‐protective group led to the phenols 15a–c, 21, 31 , and 32. The spiropiperidines 21 and 22 showed a very low affinity for the phencyclidine binding site of the NMDA receptor. In mice weakly sedative effects were caused by application of 21 and 22 .