The influence of introducing substituents of increasing bulk in α position of tetracyclic imidazoline-fused heteroazepinones on the course of hydrated imidazoline ring expansion (HIRE) reaction was established. Under certain conditions, substituted β-aminoethanols can be used to obtain solely the ring expanded products from dibenzo[b,f][1,4]ox(thi)azepin-11(10H)-ones while with their unsubstituted counterparts, side chain expulsion was the only observable outcome.