Synthesis of 3-alkylamino-3-(2-hydroxyaryl)-1-polyfluoroalkylprop-2-en-1-ones and 2-polyfluoroalkyl-4H-chromen-4-imines

Condensation of Schiff"s bases (prepared from 2-hydroxy- or 2-hydroxy-5-methylacetophenones and primary amines) with ethyl polyfluoroalkanoates in the presence of LiH in THF affords 3-alkylamino-3-(2-hydroxyaryl)-1-polyfluoroalkylprop-2-en-1-ones, which undergo cyclization in acidic media into 2-polyfluoroalkyl-4H-chromen-4-iminium salts. When neutralized with aqueous ammonia, the latter give 2-polyfluoroalkyl-4H-chromen-4-imines in high yields.