Lithium borohydride → 6-(4-Hydroxy-3-methyl-but-2-enyl)-5-methoxy-4-methyl-7-(2-trimethylsilanyl-ethoxy)3H-isobenzofuran-1-one

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A solution of 4-[6-methoxy-7-methyl-3-oxo-4-(2-trimethylsilanyl-ethoxy)-1,3-dihydro-isobenzofuran-5-yl]-2-methyl-but-2-enal (103 mg, 0.27 mmol) in methanol (5 mL) was cooled to 0° C. A solution of CeCl3 (0.68 mL, MeOH:H2O, 9:1) was added, followed by LiBH4 (0.14 mL, 0.28 mmol of a 2M solution in THF). The ice bath was removed and the reaction mixture was allowed to warm to room temperature. The reaction mixture was stirred for an additional 40 minutes whereupon TLC indicated complete consumption of starting aldehyde. The reaction was worked up by addition of aqueous 1N HCl (0.5 mL) and the product was extracted with CH2Cl2. The organic layer was washed with saturated aqueous sodium bicarbonate solution and brine. The organic layer was concentrated under reduced pressure and the residue was purified by silica gel chromatography to provide 100 mg (97%) of the product as a clear liquid. 1H NMR (300 MHz, CDCl3) δ 0.00 (s, 9H), 1.20 (dd, 2H, J=7, 8 Hz), 1.81 (s, 3H), 2.13 (s, 3H), 3.38-3.50 (m, 2H), 3.74 (s, 3H), 3.95 (s, 2H), 4.27 (dd, 2H, J=7, 8 Hz), 5.08 (s, 2H), 5.17-5.44 (m, 1H) ppm.

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