Intramolecular cyclisation of arylalkyl isothiocyanates. Part I. Synthesis of 1-substituted 3,4-dihydroisoquinolines

Abstract

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-1(2H)-thione. They are useful starting materials for the synthesis of other 1-substituted 3,4-dihydroisoquinolines, e.g. 1-amino-compounds.