Thiophenol-mediated improvement of the Pictet–Spengler cyclization of N-tosyl-β-phenethylamines with aldehydes

The Lewis acid-catalyzed Pictet–Spengler condensation of N-tosyl-β-phenethylamines with aldehydes is improved by the addition of thiophenol, furnishing better yields of 1-substituted tetrahydroisoquinolines at a given time.