Methanol → [6-Ethyl-7-methyl-3-oxo-4-(2-trimethylsilanyl-ethoxy)-1,3-dihydro isobenzofuran-5-yl]-acetaldehyde

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A solution of 6-allyl-5-ethyl-4-methyl-7-(2-trimethylsilanyl-ethoxy)-3H-isobenzofuran-1-one (261 mg, 0.788 mmol) in MeOH (5 mL), CH2Cl2 (5 mL) and pyridine (50 μL) was cooled to −78° C. using a dry ice/acetone bath according to the procedure of Smith, D. B. et al., J. Org. Chem., 1996, 61, 6, 2236. A stream of ozone was bubbled through the reaction via a gas dispersion tube until the reaction became blue in color (15 minutes). The ozone line was replaced with a stream of nitrogen and bubbling continued for another 15 minutes, by which time the blue color had disappeared. To this solution at −78° C. was added thiourea (59.9 mg, 0.788 mmol) in one portion, and the cooling bath was removed. The reaction was allowed to warm to room temperature and stirred for 15 hours. The reaction mixture was filtered and then partitioned between CH2Cl2 and water. The aqueous layer was extracted with CH2Cl2 one more time and the organic extracts were combined, washed with aqueous 1N HCl, saturated NaHCO3 and brine and dried over sodium sulfate. Filtration and evaporation of solvents in vacuo yielded the crude product, which was purified by silica gel chromatography to afford 181 mg (69%) of the product as a white solid. 1H NMR (300 MHz, CDCl3): δ=0.04 (s, 9H), 1.11 (t, J=7.5 Hz, 3H), 1.19 (m, 2H), 2.21 (s, 3H), 2.66 (q, J=7.5 Hz, 2H), 3.90 (s, 2H), 4.36 (m, 2H), 5.18 (s, 2H), 9.71 (s, 1H) ppm.

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