Abstract The reaction of 6‐aminopyrimidines 1a, b with dimedone ( 2 ) and p ‐substituted benzaldehydes 3a‐d in ethanol afforded in all cases new regiospecific synthesis of tricyclic, linear 5‐aryl‐5,6,7,8,9,10‐hexahydropyrimido[4,5‐ b ]quinolines 4a‐h in good yields. The linear structures and hence the regiospecificity of the reaction were established by nmr measurements.