Lewis acid mediated cyclisation of β-phenylethylamides with an unactivated benzene ring: an efficient preparation of dihydroisoquinolines

The efficient Lewis acid assisted cyclisation of β-phenylethylamide into dihydroisoquinolines was optimised in relation to metal chloride catalyst, and by X-ray crystallography a new type of non-bonded interaction in the cyclic systems was demonstrated: face coordination of the Cl-anion and an electron deficient pyridinium π-system.