PMR spectral study of the protonation of N,N-disubstituted 3-amino-2-aryl-1-indenones

1. N,N-disubstituted 3-amino-2-aryl-1-indenones are protonated by perchloric and trichloroacetic acids in deuteroacetone at C2 with the formation of the corresponding 3-oxo-2-aryl-1-indaniminium salts. 2. An increase in the barrier to the hindered internal rotation about the C-N bond in N,N-disubstituted 3-amino-2-aryl-l-indenones is observed with a decrease in the extent of the C2-protonation of these compounds.