Quinazolines. XI. Synthesis of 2,4‐diamino‐5, 10‐diliydrobenzo[g] quinazolines

An unequivocal synthesis of 2,4‐diamino‐5,10‐dihydrobenzo[g]quinazolines is described, starting from methyl 2‐tetralone‐3‐carboxylates. Condensation with guanidine yielded 2‐amino‐4‐hydroxy derivatives, which were thiated with phosphorus pentasulfide and S‐alkylated with dimethyl sulfate. The resultant 2‐amino‐4‐methylthio compounds were converted into 2,4‐diamino derivatives by amination at elevated temperature and pressure. Attempted synthesis from 3‐cyano‐1,4‐dihydro‐2‐methoxynaphthalene and guanidine was unsuccessful.