Saturated heterocycles. 57 . Synthesis of 4‐substituted‐9,10‐dialkoxy‐1,6,7,11b‐tetrahydro‐2 H ‐pyrimido[6,1‐ a ]isoquinolin‐2‐ones

A large number of 4‐substituted‐9,10‐dialkoxy‐1,6,7,11b‐tetrahydropyrimido[6,1‐ a ]isoquinolin‐2‐ones were prepared by the reaction of 1‐(ethoxycarbonylmethyl)‐6,7‐dialkoxy‐1,2,3,4‐tetrahydroisoquinolines with iminoethers. Reaction of the corresponding isoquinoline‐1‐acetic acid derivatives with iminoethers led to the formation of N ‐acyl‐1,2,3,4‐tetrahydroisoquinolin‐1‐acetamides. In the hydrolysis of the prepared 4‐substituted‐pyrimido[6,1‐ a ]isoquinolin‐2‐ones, the corresponding N ‐acyl‐1,2,3,4‐tetrahydroisoquinolin‐1‐acetamides were obtained. While reduction of the 4‐phenyl derivative resulted in the corresponding 1,3,4,6,7,11b‐hexahydropyrimidinone. The steric structures of the tetrahydro‐ and hexahydropyrimido[6,1‐ a ]isoquinolines were determined by nmr spectroscopy.