With triethyloxonium tetrafluoroborate or ethyl or methyl fluorosulphonate, 2-arylethyl isothiocyanates cyclised to give a 1 -ethylthio-or 1 -methylthio-3,4-dihydroisoquinoline, respectively. These compounds were prepared also by successive cyclisation of the isothiocyanates with aluminium chloride or polyphosphoric acid and alkylation of the resultant 3,4-dihydroisoquinoline-? (2H) -thione. They are useful starting materials for the synthesis of other 1 -substituted 3,4-dihydroisoquinolines, e.g. 1 -amino-compounds.?At approximately the time our first patent application 2 was published another appeared in which compounds (12), ( 14), and the hydroiodide of compound (1 7) are described along with several l-amino-3,4-dihydroisoquinolines [C.

Bei der Umsetzung des Isocyanats (I) mit Methyl‐fluorsulfonat bzw. Triäthyloxonium‐tetrafluoroborat entstehen direkt die entsprechenden Isochinoliniumsalze (II), aus denen die freien Basen (III) gewonnen werden.