A Novel Synthesis of Biologically Active Perfluoroalkyl N-Heterocyclic Compounds Using Organosilicon Reagents

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N-Silyl-l-aza-allyl anions (1), generated from 3-methyl-5-(trimethylsilylmethyl)-isoxazole and aryl cyanides, reacted with perfluoro(2-methyl-2-pentane) (2) or 3-acethyl-4-methoxy-3-buten-2-one (3) to give the corresponding Rf or 4-Me pyridines (4) or (5) in high yields. The former product (4) was effectively converted into the corresponding 1,6-naphthyridine in good yield by hydrogenation of the isoxazole ring and the consecutive intramolecular cyclization in the presence of sodium hydoxide. On the other hand, 2-(Trimethylsilylmethyl)pyridine reacted with (2) in the presence of potassium fluoride to afford 2-pentafluoroethyl-3-trifluoromethyl-4H-quinolizin-4-one (6) in quantitative yield. The analogous reaction of the silyl derivatives of methylpyridines, methylquinolines, benzoxazole and benzothiazole gave the corresponding Rf-substituted compounds in good yields. The compound (6), furthermore, gave the methyl ester of the 3-carboxylic acid of (6) in high yield on treating with dimethyl sulfate whereas (6) quantitatively gave 2-pentafluoroethyl-4H-quinolizin-4-one (7) by decarboxylation after hydrolysis on treating with sulfuric acid. The mechanisms of these reactions were also discussed.