Efficient and convenient entry to β-hydroxy-β-trifluoromethyl-β-substituted ketones and 2,6-disubstituted 4-trifluoromethylpyridines based on the reaction of trifluoromethyl ketones with enamines or imines
The reactions of trifluoromethyl ketones with enamines or imines are described. The reaction of trifluoroacetone with enamines or imines followed by hydrolysis gave the corresponding β-hydroxy-β-trifluoromethyl-β-methyl ketones in good yields. The reaction of trifluoromethylated β-diketones with enamines in the presence of ammonium acetate gave 4-trifluoromethylated pyridines exclusively in good yields, without any detectable amount of regioisomers.
Synthesis of 4-Trifluoromethylpyridines by [5+1] Cyclization of 3-Hydroxy-pent-4-yn-1-ones with Urea
作者:Viktor O. Iaroshenko、Dmytro Ostrovskyi、Khurshid Ayub、Anke Spannenberg、Peter Langer
DOI:10.1002/adsc.201200687
日期:——
alkynylation reactions which are not possible for alkyl- or aryl-substituted derivatives. The products can be easily transformed into 2,6-diaryl-4-trifluoromethylpyridines by acid-mediated [5+1] cyclization with urea. The reaction was thoroughly optimized by variation of the conditions and the scope was studied in detail. The products are not readily available by other methods. A plausible mechanism was