Synthesis of 1,2,3,4-Tetrahydroisoquinolines

Article abstract of DOI:10.1021/jo00134a025

Several aspects of 1,2,3,4-tetrahydroisoquinoline synthesis have been examined.An improved synthesis of 2-(m-methoxyphenyl)ethylamine (4) is reported. m-Anisaldehyde (5) was treated with potassium cyanide and ethyl chloroformate to yield O-(ethoxycarbonyl)-3-methoxymandelonitrile (7).Hydrogenation afforded 2-(m-methoxyphenyl)ethylamine (4) in 87percent yield overall.Some observations have been made regarding the reduction of 3,4-dihydroisoquinolines derived from the Bischler-Napieralski reaction.Amides 3a and 3c were cyclized with phosphorus oxychloride, followed by reduction to the corresponding tetrahydroisoquinolines 1a and 1c.It was shown that 1a and 1c were contaminated with 4percent of 2a and 3percent of 2c, respectively.Both 2a and 2c were independently synthesized by routes with general applicability to 8-alkoxy-1,2,3,4-tetrahydroisoquinolines.