Abstract: We have explored the use of steric hindrance on controlling the ring-chain tautomeric equilibrium of a tetrahydroquinazoline/imine system. Two imines, one of them having a bulky group (E)-N (3-((2-((4-methylphenylsulfonamido)methyl)phenylimino)methyl)pyridin-2-yl)pivalamide (H2L1SB) and the other one without bulky group (E)-N-(2-(2,3-dihydroxybenzylideneamino)-benzyl)-4-methylbenzenesulfonamide (H2L2SB) have been synthetised and spectroscopically studied by 1H NMR. Besides, the formation of the corresponding 1,2,3,4-tetrahydroquinazolines (H2L1TQ and H2L2TQ) was tested.