Pyridine → 8-Methyl-1,4-dioxa-spiro[4,5]decane-8-carbaldehyde

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Under a nitrogen atmosphere, solid chromium (IV) oxide (84.7 mmol, 8.47 g, 6.6 eq.) was added to a stirred solution of extra dry pyridine (171 mmol, 14.53 mL, 13.3 eq.) in dry methylene chloride (123 mL) cooled to 0° C. in an ice bath. The resulting solution was stirred at room temperature for 15 minutes. To this mixture was then added a solution of 4 (12.83 mmol, 2.28 g) in dry methylene chloride (19 mL) and the resulting mixture was stirred at room temperature for 30 minutes. The reaction mixture was then decanted into a seperatory funnel and the residue was washed with ethyl ether (40 mL and 50 mL). The washings were combined and the organic layer was washed with 5% aqueous sodium hydroxide solution (2×40 mL), 5% aqueous hydrochloric acid solution (3×40 mL), saturated aqueous sodium bicarbonate solution (3×40 mL) and brine (3×40 mL), then dried over magnesium sulfate, filtered, and concentrated in vacuo to give 5 (12.24 mmol, 2.35 g, 95%) as an amorphous solid. The product was used in the next reaction without further purification: 1H NMR (CDCl3) δ 9.47 (1H, s), 3.95 (4H, s), 2.00-1.96 (2H, m), 1.71-1.67 (2H, m), 1.61-1.53 (4H, m), 1.05 (s, 3H); 13C NMR (CDCl3) δ 205.9, 108.4, 64.4, 64.4, 45.7, 31.4, 29.9, 21.2.

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