Cool the solution containing compound III (74.4g, 0.255mol containing compound III) to -100, and add 120g of sulfuric acid with a mass fraction of 92.5% to the above system while keeping the temperature below 0. After acidification, continue to react and keep for 1.5h, and then add 126.7g of 33% sodium nitrite aqueous solution (containing diazotizing reagent sodium nitrite 0.612mol) into the system uniformly within 2h, and keep the temperature at 0 The following reaction is carried out for 2 hours, and the system is heated to room temperature after full reaction, 111.1 g of 50% hypophosphorous acid and 0.67 g of cuprous oxide are added, and the reaction is stirred for 2 hours while keeping temperature. After the reaction is over, stand to separate the layers, and wash the organic layer with a 5% sodium bicarbonate aqueous solution, dry with anhydrous magnesium sulfate, and rectify to obtain a clear and transparent oily liquid 1-[3-chloro-5-(trifluoromethyl) (Yl)phenyl]-2,2,2-trifluoroethanone 66.9, content 99.5%, yield 87.2%.
