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At 0° C., cycloheptanone (1) (5 cm3, 42.61 mmol, 1 eq.), trimethylorthoformate (5.2 cm3, 46.88 mmol, 1.1 eq.) and anhydrous toluenesulphonic acid (40 mg, 0.213 mmol, 0.05 eq.) were allowed to warm to room temperature and left to stand for 2 days. Crude 1H-NMR spectroscopy indicated formation of the intermediate ketal. Distillation, initially at atmospheric pressure, then at water aspirator pressure (ca. 15 mm/Hg) afforded the product 2 (3.82 g, 71%) as a colourless liquid (b.p. 130-140° C./15 mm/Hg). δH (250 MHz, CDCl3) 1.35-1.55 (4H, m, CH), 1.59-1.74 (2H, m, CH2), 1.97-2.08 (2H, m, CH2), 2.12-2.25 (2H, m, CH2), 3.39 (3H, s, CH3), 4.67 (1H, t, J 7.0 Hz, CH); m/z (CI) 127 (MH+, 100%).

1. customAt 0° C.
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3. distillationDistillation