Synthesis of 4‐Trifluoromethylpyridines by [5+1] Cyclization of 3‐Hydroxy‐pent‐4‐yn‐1‐ones with Urea

Abstract Trifluoromethyl‐substituted 1,3‐diketones can undergo direct 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 suggested based on DFT calculations.