Abstract
Palladium-catalyzed coupling of arylamines and 2-bromo-3,3,3-trifluoropropene (BTP) was investigated. When a toluene solution of aniline and BTP was heated at 110 °C in the presence of Pd 2(dba) 3·CHCl 3, 1,1′-diphenylphosphinoferrocene and Cs 2CO 3 under an argon atmosphere, N-(1,1,1-trifluoro-2-propylidene)aniline was obtained in excellent GC and 19F NMR yields (99%) and isolated yield (92%). Cs 2CO 3 was exclusively effective in the coupling reaction among the bases tested. The coupling using 2-aminobenzonitriles as substrates provided not only 2- N-(1,1,1-trifluoro-2-propylidene)aminobenzonitriles but also 4-amino-2-trifluoromethylquinolines and 2-trifluoromethyl-4- N-(1,1,1-trifluoro-2-propylidene)aminoquinolines. The strong electron-withdrawing character of CF 3 will enhance the acidity of the methyl proton in the N-(1,1,1-trifluoromethyl-2-propylidene)amino group, resulting in the attack of the methyl proton to the carbon in the cyano group to give 4-amino-2-trifluoromethylquinolines. Moreover, the one-pot synthesis of 2-trifluoromethylindoles with 2-bromoanilines and BTP was achieved by use of Pd(OAc) 2, 2-dicyclohexylphosphino-2′,4′,6′-triisopropylbipenyl and Cs 2CO 3. The Pd-catalyzed intramolecular Heck coupling of the vinyl group in 2-bromo- N-(1-trifluoromethyl)vinylanilines, which is the tautmeric isomer of 2-bromo- N-(1,1,1-trifluoro-2-propylidene)anilines, and the C Br bond presumably furnished indole rings. The C N double bond of N-(1,1,1-trifluoro-2-propylidene)amino group obtained here was smoothly hydrogenated to N-(1-methyl-2,2,2-trifluoro)ethylamino group using LiAlH 4 or H 2 with Pd/C.
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