[CH2:1]([O:3][CH:4]=[CH:5][C:6](=[O:11])[C:7]([F:10])([F:9])[F:8])[CH3:2].C(O)C[OH:14]>C1(C)C=CC=CC=1.O.CC1C=CC(S(O)(=O)=O)=CC=1>[O:3]1[CH2:1][CH2:2][O:14][CH:4]1[CH2:5][C:6](=[O:11])[C:7]([F:9])([F:10])[F:8]4-Methylbenzenesulfonic acid monohydrate (500.1 mg, 467.4 μL, 2.629 mmol) was added to a solution of 4-ethoxy-1,1,1-trifluoro-but-3-en-2-one (200.97 g, 1.195 mol) and ethylene glycol (77.27 g, 69.42 mL, 1.245 mol) in toluene (502.5 mL). The reaction mixture was heated to reflux for 90 min (oil bath). Then, the reflux was continued with simultaneous distillation of ethanol/toluene. The Dean-Stark was removed and the flask was connected to a distillation apparatus. 3-(1,3-Dioxolan-2-yl)-1,1,1-trifluoro-propan-2-one was distilled using a KNF pump (Bp 81° C.) as a light yellow oil (148 g, 67% yield). 1H NMR (500 MHz, CDCl3) δ 5.38-5.40 (t, 1H), 4.02-4.05 (m, 2H), 3.93-3.95 (m, 2H), 3.10 (d, 2H).
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