2-Benzopyrylium salts. 44. Formation of 4-acyl-3,4-dihydroisoquinolinium salts from the reaction of 2-benzopyrylium salts with azomethines and the cycloaddition of male-imides to the product of their deprotonation, the 2,3-dihydroisoquinolines
The effect of substituents in the 2-benzopyrylium cation and in the azomethines on the character of their reaction in various solvents has been clarified. It was shown that the 4-acyl-3,4-dihydroisoquinolinium salts resulting after deprotonation form compounds with an ortho-quinonoid structure which then react with maleimides by cycloaddition.