Synthesis of polyfluoroalkoxylated pyrimidines and pyrazoles by using novel β-polyfluoroalkoxy vinamidinium salts

Novel beta-polyfluoroalkoxy vinamidinium salts 3 and/or 4 were prepared in good yields by the reaction of N-( 2-polyfluoroalkoxy-3,3-difluoro-1-propenyl) trimethylammonium iodides (2) with secondary amines in acetonitrile at 70 degrees C for 1 h. These vinamidinium salts readily reacted with bifunctional heteronucleophiles, such as amidines, guanidines and hydrazines, to give regiospecifically polyfluoroalkoxylated pyrimidines (6) and pyrazoles (8) in good yields. The one-pot procedure starting from N-(2,3,3-trifluoro-1-propenyl) trimethylammonium iodide (1), which was the precursor of 2, was applicable for synthesizing the heterocyclic compounds in almost comparable yields with those obtained by the stepwise procedure using isolated 3 and 4. (C) 1998 Elsevier Science S.A. All rights reserved.