Carbenium Ions in Substitution Reactions at the Amino Nitrogen Atom

Tropylium, xanthylium, and tritylium salts characterized by different stabilities differently reacted with biologically active amines. The reactions of tropylium perchlorate and tetrafluoroborate with 4-(cyclohepta-2,4,6-trien-1-yl)aniline was accompanied by hydrolysis of the N-(cyclohepta-2,4,6-trien-1-yl) derivative, the N-xanthenyl derivative underwent dehydrogenation, whereas tritylium perchlorate failed to react with 4-(cyclohepta-2,4,6-trien-1-yl)aniline. The reactions of pyrimidin-2-amine with tropylium, xanthylium, and tritylium salts afforded products of substitution of one hydrogen atom in the amino group with high yields. The N-substituted pyrimidin-2-amine derivatives were stable, and neither their dehydrogenation nor hydrolysis was observed.