Selective and efficient structural elaboration of 2-(trifluoromethyl)quinolinones

The acid-catalyzed cyclization-condensation between anilines and Et 4,4,4-trifluoroacetoacetate affords 1,4-dihydro-2-trifluoromethyl-4H-4-quinolinones, which can easily be converted into 4-bromo-2-(trifluoromethyl)quinolines. These undergo halogen/metal exchange, generating 2-trifluoromethyl-4-quinolyllithiums, when treated with butyllithium, and hydrogen/metal exchange, generating 4-bromo-2-trifluoromethyl-3-quinolyllithiums, when treated with lithium diisopropylamide. Trapping of the latter intermediates provides 3-functionalized products that may be further elaborated by electrophilic substitution of the bromine atom. A few unexpected findings resulted from these investigations, the most noteworthy being an unprecedented buttressing effect and a counterintuitive halogen reactivity. [on SciFinder (R)]