Ethyl Acetate → N-(6-Bromo-5',6'-dihydro-4'H-spiro[chromene-2,3'-pyran]-4(3H)-ylidene)-2-methylpropane-2-sulfinamide

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6-Bromo-5′,6′-dihydro-4′H-spiro[chromene-2,3′-pyran]-4(3H)-one (Intermediate 26, 2.007 g, 6.75 mmol), 2-methylpropane-2-sulfinamide (1.228 g, 10.13 mmol) and titanium ethoxide (2.78 mL, 13.51 mmol) were dissolved in methyl THF (16 mL) and heated to reflux for 19 h. The reaction was left to cool down to r.t. when EtOAc (80 mL) and NaHCO3 (sat., 5 mL) were added under stirring. The mixture was let standing for 1 h. The organic phase was collected by filtration, dried over MgSO4 and concentrated. The crude product was purified by flash chromatography using a gradient of 0-50% EtOAc in heptane. The desired fractions were evaporated to give the title compound as a mixture of diastereomers in a ratio 1:1 as determined by NMR (2.63 g, 97% yield): 1H NMR (500 MHz, CDCl3) δ ppm 1.34 (s, 9H), 1.50-1.57 (m, 0.5H), 1.60-1.68 (m, 1H), 1.73 (m, 0.5H) 1.87-2.09 (m, 2H), 2.99 (d, 0.5H), 3.26 (d, 0.5H), 3.33 (d, 0.5H), 3.45-3.61 (m, 2H), 3.64 (d, 0.5H), 3.77-3.93 (m, 2H), 6.88-6.93 (m, 1H), 7.48 (dd, 1H), 7.98 (dd, 1H); MS (ES+) m/z 401.9 [M+H]+.

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