A new one-pot synthesis of 3,4-dihydroquinazolines by diethyl azodicarboxylate (DEAD)-promoted oxidative Ugi/ aza-Wittig reaction was developed. The reactions of iminophosphoranes 5, N-aryl-1,2,3,4-tetrahydroisoquinolines 6 and acids 7 produced 3-(tetrahydroisoquinolin-1-formyl) substituted 3,4-dihydroquinazolines 8 in moderate to good yields in the presence of DEAD by tandem oxidative Ugi/aza-Wittig reaction.