Synthesis of 3-Trifluoromethyl- and 3-Perfluoroalkyl-Substituted 3-Aryloxy- and 3-Heteroaryloxypropenoic Acids and of the Cyclization Products, 2-Trifluoromethyl- and 2-Perfluoroalkyl-4H-chromen-4-ones - Kharrat, Salem El; Kharrat, Rouba El; Laurent, Philippe; Blancou, Hubert (Synthesis, 2007)