Synthesis of 4-oxo-2-thioxo-1,2,3,4,5,6-hexahydrospiro(benzo[h]quinazoline-5,1′-cyclohexane and its reaction with dibromoalkanes

4-(N′-Benzoylthioureido)-3-ethoxycarbonyl-1,2-dihydrospiro(naphthalene-2,1′-cyclohexane), which was synthesized from 4-amino-3-ethoxycarbonyl-1,2-dihydrospiro(naphthalene-2,1′-cyclohexane) and benzoyl isothiocyanate, cyclized to give 4-oxo-2-thioxo-1,2,3,4,5,6-hexahydrospiro(benzo[h]quinazoline-5,1′-cyclohexane). Reaction of the latter with 1,2-dibromoethane or 1,3-dibromopropane gave products of intramolecular dialkylation at the S and N(3) atoms.