Ring-cyclized products from the Delepine reaction

Abstract

Reaction of 2-bromo-3′,5′-bisbenzyloxyacetophenone (1a) with hexamine (hexamethylenetetramine) in chlorobenzene gave an insoluble hexaminium salt which on hydrolysis with hydrochloric acid in ethanol afforded a mixture of 3′,5′-bisbenzyloxyphenacylammonium chloride (2a) and 6,8-bisbenzyloxy-4-oxo-1,2,3,4-tetra-hydroisoquinolinium chloride (3a). When ethanol-free chloroform was used as solvent for the reaction no insoluble hexaminium salt was formed and acid hydrolysis of the product gave 3-ammoniomethyl-6,8-bisbenzyloxy-4-oxo-1,2,3,4-tetrahydroisoquinolinium dichloride (3c).