Improved and Practical Synthesis of 6-Methoxy-1,2,3,4- tetrahydroisoquinoline Hydrochloride

6-Methoxy-1,2,3,4-tetrahydroisoquinoline (1) or its hydrochloride salt (4) is an expensive chemical with limited commercial availability. We report an improved and practical synthesis of 4 from inexpensive 2-(3-methoxyphenyl)ethylamine (2) using a Pictet−Spengler condensation via a novel aminal intermediate. The synthesis significantly lowers the cost and provides easy access to 6-methoxy-1,2,3,4-tetrahydroisoquinoline or its HCl salt on a large scale.