A Very Mild Access to 3,4-DihydroisoquinolinesUsing Triphenyl Phosphite-Bromine-Mediated Bischler-Napieralski-TypeCyclization

Substituted β-phenylethylamides undergo smooth intramolecular cyclization to 3,4-dihydroisoquinolines in good to excellent yields when treated with bromotriphenoxyphosphonium bromide at –60 °C in dichloromethane in the presence of triethylamine. The reaction proceeds under the mildest conditions ever reported for Bischler–Napieralski-type cyclizations. When chlorotriphenoxyphosphonium choride is used, low yields are obtained instead.