27 g of 1,2,3,4-tetrahydroisoquinoline was added at room temperature to a
solution of 28 g of 2-methyl-2-isothiourea sulfate in 80 ml of water. The
resulting mixture was kept at room temperature with occasional shaking. After
a short period of time, methylmercaptan began to escape, and the mixture
warmed up slightly. After then standing for 24 hours, crystals formed. They
were filtered off and rinsed with ice cold water. Recrystallization from
approximately 100 ml of water yielded 1,2,3,4-tetrahydroisoquinoline-2-
carboxamidine sulfate melting at 278°C to 280°C (uncorr.).
Another batch prepared in the same manner melted at 284°C to 285°C due to
a minute difference in moisture content.
Both batches prepared above analyzed correctly for (C10H13N3)2·H2SO4.
